The hardware reset value of bit CCM_CLPCR_LPM enables WAIT mode
(WAIT_UNCLOCKED) by default. However this is undesirable because
WAIT mode should only be enabled when there is a driver managing
ARM clock gating. Correct the initial power mode to WAIT_CLOCKED
(disable WAIT mode). While at it, the power mode after resuming
is also set back to WAIT_CLOCKED from STOP_POWER_OFF.