timer: mask interrupts in timer's timeout handler.

before running timer's timeout function, we need to make
sure that those threads waiting on this timer have been
added into the timer's wait queue, so add operations to
use timer lock to mask interrupts in z_timer_expiration_handler
function to synchronize timer's wait queue.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>