linux/kernel.h: split *_MAX and *_MIN macros into <linux/limits.h>

<linux/kernel.h> tends to be cluttered because we often put various sort
of unrelated stuff in it.  So, we have split out a sensible chunk of
code into a separate header from time to time.

This commit splits out the *_MAX and *_MIN defines.

The standard header <limits.h> contains various MAX, MIN constants
including numerial limits.  [1]

I think it makes sense to move in-kernel MAX, MIN constants into
include/linux/limits.h.

We already have include/uapi/linux/limits.h to contain some user-space
constants.  I changed its include guard to _UAPI_LINUX_LIMITS_H.  This
change has no impact to the user-space because
scripts/headers_install.sh rips off the '_UAPI' prefix from the include
guards of exported headers.

[1] http://pubs.opengroup.org/onlinepubs/009604499/basedefs/limits.h.html

Link: http://lkml.kernel.org/r/1549156242-20806-2-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Alex Elder <elder@linaro.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/uapi/linux/limits.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-#ifndef _LINUX_LIMITS_H
-#define _LINUX_LIMITS_H
+#ifndef _UAPI_LINUX_LIMITS_H
+#define _UAPI_LINUX_LIMITS_H
 
 #define NR_OPEN	        1024