fs: cifs: replace CURRENT_TIME by other appropriate apis

CURRENT_TIME macro is not y2038 safe on 32 bit systems.

The patch replaces all the uses of CURRENT_TIME by current_time() for
filesystem times, and ktime_get_* functions for authentication
timestamps and timezone calculations.

This is also in preparation for the patch that transitions vfs
timestamps to use 64 bit time and hence make them y2038 safe.

CURRENT_TIME macro will be deleted before merging the aforementioned
change.

The inode timestamps read from the server are assumed to have correct
granularity and range.

The patch also assumes that the difference between server and client
times lie in the range INT_MIN..INT_MAX.  This is valid because this is
the difference between current times between server and client, and the
largest timezone difference is in the range of one day.

All cifs timestamps currently use timespec representation internally.
Authentication and timezone timestamps can also be transitioned into
using timespec64 when all other timestamps for cifs is transitioned to
use timespec64.

Link: http://lkml.kernel.org/r/1491613030-11599-4-git-send-email-deepa.kernel@gmail.com


Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>