drm/lima: power down ip blocks when pmu exit

Prepare resume/suspend PM.

v2:
Fix lima_pmu_wait_cmd timeout when mali400 case.

Tested-by: Bhushan Shah <bshah@kde.org>
Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200421133551.31481-7-yuq825@gmail.com