staging/lustre: use 64-bit times in debug print

This adapts the format string and get_seconds() call to not
overflow in 2038 in the libcfs_debug_dumplog_internal()
function.

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>