ENGR00210850 mx6: boot failure with local timer and wait mode enabled

ENGR00210850 mx6: boot failure with local timer and wait mode enabled

Previous patch only check the condition that GPT broadcast
event is ready or not before doing clock event switch.
It's not enough, as the clock switch from local timer to GPT
broadcast must be happen after GPT broadcast clock event setup
and current cpu's clock device switch to local timer clock event.
Otherwise, we will have chance that cpu exit the wait mode and
switch back clock event without local timer event setup correctly.

Signed-off-by: Xinyu Chen <xinyu.chen@freescale.com>