drm/radeon: fix reversed logic in evergreen_mc_resume

Need to unblank the display when resuming the MC.  No
functional change as this code path is not currently
hit.  We always disable the displays entirely rather
than just blanking them.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/evergreen.c
Simple merge