Add support for CLOCK_TAI in timetests

With CLOCK_TAI landing in 3.10, add support for the
new clockid in the timetests

Signed-off-by: John Stultz <john.stultz@linaro.org>
Cleanup mqueue-lat.c

mqueue-lat has a bunch of boilerplate code that is unused,
so remove it.

Signed-off-by: John Stultz <john.stultz@linaro.org>