drm/msm: Do rpm get sooner in the submit path

Unfortunately, due to an dev_pm_opp locking interaction with
mm->mmap_sem, we need to do pm get before aquiring obj locks,
otherwise we can have anger lockdep with the chain:

  opp_table_lock --> &mm->mmap_sem --> reservation_ww_class_mutex

For an explicit fencing userspace, the impact should be minimal
as we do all the fence waits before this point.  It could result
in some needless resumes in error cases, etc.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>