LU-4423 ldlm: use 64-bit time for pl_recalc

LU-4423 ldlm: use 64-bit time for pl_recalc

The ldlm pool calculates elapsed time by comparing the previous and
current get_seconds() values, which is unsafe on 32-bit machines
after 2038.

This changes the code to use time64_t and ktime_get_real_seconds(),
keeping the 'real' instead of 'monotonic' time because of the
debug prints.

Linux-commit: 8f83409cf2382c968f96877368cd5b542b92af1d
Linux-commit: b8cb86fd95bb461c3496e1f4b4083b198c963a9c

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Change-Id: I81cca5b529dbf5615cf46461ad1c9179fdee7835
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/23350
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>