ENGR00180537 [MX6]Fix standby unstable issue

ENGR00180537 [MX6]Fix standby unstable issue

For the standby mode, we force SOC enter STOP mode
and drop the VDDARM_IN and VDDSOC_IN to 0.9V, we need
to disable L1 and L2 cache and invalidate L1 cache when
system resume, as the L1 cache memory's power is dropped
during standby, need to do the invalidation before re-enable
it.

Signed-off-by: Anson Huang <b20788@freescale.com>