ENGR00217946 VPU kernel driver: fix suspend/resume i.MX6DL hang issue

ENGR00217946 VPU kernel driver: fix suspend/resume i.MX6DL hang issue

Bug: VPU easily hang during suspend/resume standby mode i.MX6Q/i.MX6DL

Fix: standby mode doesn't power off/on PU but changes voltage instead, thus
VPU requires a reset cause there's always chance some cell is on
unstable state after voltage change

suspend/resume DSM is OK because it power off/on PU and probably there is a
power-on-reset sequence embedded in SOC

Signed-off-by: Hongzhang Yang <Hongzhang.Yang@freescale.com>