LU-13344 sec: remove time_t usage

LU-13344 sec: remove time_t usage

In the latest kernels time_t has been removed since time_t has
been a 64 bit value just like time64_t so no need for it anymore.
Change ps_sepol_mtime to ktime_t which is the preferred time
format in the linux kernel. For the case of the Lustre GGS code
the fields marked as time_t are timestamps so just change it to
time64_t.

Change-Id: I9f40592d440cc8d68c7b73c0c31d88bcecb3723b
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/37942
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Tested-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>