unified: Add missing arguments to K_TIMER_DEFINE()

It is now possible to specify the expiry and stop functions
of a statically-defined timer, just as can be done for a
dynamically-defined timer.

[Part of fix to ZEP-1186]

Change-Id: Ibb9096f3fdafdc6c904184587f86ecd52accdd66
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>