drm/radeon/kms: reorder display resume to avoid problems

On resume, we were attemping to unblank the displays before the
timing and plls had be reprogrammed which led to atom timeouts
waiting for things that are not yet programmed.  Re-program
the mode first, then reset the dpms state.

This fixes the infamous atombios timeouts on resume.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>