lustre: Use long long type to print inode time

Subsequent patches in the series convert inode timestamps
to use struct timespec64 instead of struct timespec as
part of solving the y2038 problem.

Convert these print formats to use long long types to
avoid warnings and errors on conversion.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
CC: andreas.dilger@intel.com