[MIPS] Wire up the timerfd_*() o32 system calls

This patch enables the system calls timerfd_create(), timerfd_settime()
and timerfd_gettime() for MIPS architecture.

Please see the following Bugzilla entry for more details:

http://bugzilla.kernel.org/show_bug.cgi?id=10038

This was tested using a Malta 4Kc board in both little-endian and
big-endian modes. The unit test program is available from the URL
above.

Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@gmail.com>

[Ralf: Added N64, N32 and O32 bits on 64-bit kernels.]
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>