staging/lustre: use 64-bit inode timestamps internally

Lustre has 64-bit timestamps in its network data structures, but
on 32 bit systems, it converts them directly into time_t, which is
32 bit wide.

This changes the code to use 64-bit time stamps for files. The Linux
VFS code still uses time_t though, and will be changed in a separate
patch series.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>