Move the pcf8591 driver to hwmon

Directory drivers/i2c/chips is going away, so drivers there must find
new homes. For the pcf8591 driver, the best choice seems to be the
hwmon subsystem. While the Philips PCF8591 device isn't a typical
hardware monitoring chip, its DAC interface is compatible with the
hwmon one, so it fits somewhat.

If a better subsystem is ever created for ADC/DAC chips, the driver
could be moved there.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Aurelien Jarno <aurelien@aurel32.net>

Documentation/i2c/chips/pcf8591

@@ -1,90 +0,0 @@
-Kernel driver pcf8591
-=====================
-
-Supported chips:
-  * Philips PCF8591
-    Prefix: 'pcf8591'
-    Addresses scanned: I2C 0x48 - 0x4f
-    Datasheet: Publicly available at the Philips Semiconductor website
-               http://www.semiconductors.philips.com/pip/PCF8591P.html
-
-Authors:
-        Aurelien Jarno <aurelien@aurel32.net>
-        valuable contributions by Jan M. Sendler <sendler@sendler.de>,
-        Jean Delvare <khali@linux-fr.org>
-
-
-Description
------------
-The PCF8591 is an 8-bit A/D and D/A converter (4 analog inputs and one
-analog output) for the I2C bus produced by Philips Semiconductors. It
-is designed to provide a byte I2C interface to up to 4 separate devices.
-
-The PCF8591 has 4 analog inputs programmable as single-ended or
-differential inputs :
-- mode 0 : four single ended inputs
-        Pins AIN0 to AIN3 are single ended inputs for channels 0 to 3
-
-- mode 1 : three differential inputs
-        Pins AIN3 is the common negative differential input
-        Pins AIN0 to AIN2 are positive differential inputs for channels 0 to 2
-
-- mode 2 : single ended and differential mixed
-        Pins AIN0 and AIN1 are single ended inputs for channels 0 and 1
-        Pins AIN2 is the positive differential input for channel 3
-        Pins AIN3 is the negative differential input for channel 3
-
-- mode 3 : two differential inputs
-        Pins AIN0 is the positive differential input for channel 0
-        Pins AIN1 is the negative differential input for channel 0
-        Pins AIN2 is the positive differential input for channel 1
-        Pins AIN3 is the negative differential input for channel 1
-
-See the datasheet for details.
-
-Module parameters
------------------
-
-* input_mode int
-
-    Analog input mode:
-         0 = four single ended inputs
-         1 = three differential inputs
-         2 = single ended and differential mixed
-         3 = two differential inputs
-
-
-Accessing PCF8591 via /sys interface
--------------------------------------
-
-! Be careful !
-The PCF8591 is plainly impossible to detect ! Stupid chip.
-So every chip with address in the interval [48..4f] is
-detected as PCF8591. If you have other chips in this address
-range, the workaround is to load this module after the one
-for your others chips.
-
-On detection (i.e. insmod, modprobe et al.), directories are being
-created for each detected PCF8591:
-
-/sys/bus/devices/<0>-<1>/
-where <0> is the bus the chip was detected on (e. g. i2c-0)
-and <1> the chip address ([48..4f])
-
-Inside these directories, there are such files:
-in0, in1, in2, in3, out0_enable, out0_output, name
-
-Name contains chip name.
-
-The in0, in1, in2 and in3 files are RO. Reading gives the value of the
-corresponding channel. Depending on the current analog inputs configuration,
-files in2 and/or in3 do not exist. Values range are from 0 to 255 for single
-ended inputs and -128 to +127 for differential inputs (8-bit ADC).
-
-The out0_enable file is RW. Reading gives "1" for analog output enabled and
-"0" for analog output disabled. Writing accepts "0" and "1" accordingly.
-
-The out0_output file is RW. Writing a number between 0 and 255 (8-bit DAC), send
-the value to the digital-to-analog converter. Note that a voltage will
-only appears on AOUT pin if aout0_enable equals 1. Reading returns the last
-value written.