ceph: make inode time prints to be long long

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: zyan@redhat.com
Cc: ceph-devel@vger.kernel.org