ptp: deprecate gettime64() in favor of gettimex64()

When a driver provides gettimex64(), use it in the PTP_SYS_OFFSET ioctl
and POSIX clock's gettime() instead of gettime64(). Drivers should
provide only one of the functions.

Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ptp_clock_kernel.h

@@ -82,6 +82,8 @@ struct ptp_system_timestamp {
  *            parameter delta: Desired change in nanoseconds.
  *
  * @gettime64:  Reads the current time from the hardware clock.
+ *              This method is deprecated.  New drivers should implement
+ *              the @gettimex64 method instead.
  *              parameter ts: Holds the result.
  *
  * @gettimex64:  Reads the current time from the hardware clock and optionally