compat: Enable compat_get/put_timespec64 always

These functions are used in the repurposed compat syscalls
to provide backward compatibility for using 32 bit time_t
on 32 bit systems.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>