This adds a adjtimex validation test which checks the behavior
for a set of valida and invalid inputs. So far this only tests
ADJ_FREQUENCY, but hopefully will grow.

Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Tested-by: NPrarit Bhargava <prarit@redhat.com>
Signed-off-by: NShuah Khan <shuahkh@osg.samsung.com>