LU-11838 ldlm: struct timespec64.tv_sec type change

LU-11838 ldlm: struct timespec64.tv_sec type change

Since kernel 4.18 struct timespec64 is no longer defined
as struct timespec on 64bit systems, this means tv_sec
is no longer __kernel_time_t but now time64_t.

Use %llu as the format specifier and explicitly cast it
to unsigned long long.

Test-Parameters:trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: Ib4c80c9b20854d45b1b3c04057c45ee20d5413d9
Reviewed-on: https://review.whamcloud.com/34677
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>