drm/amd/display: Fix DFPstate hang due to view port changed

drm/amd/display: Fix DFPstate hang due to view port changed

[Why]
Place the cursor in the center of screen between two pipes then
adjusting the viewport but cursour doesn't update cause DFPstate hang.

[How]
If viewport changed, update cursor as well.

Cc: stable@vger.kernel.org
Signed-off-by: Paul Hsieh <paul.hsieh@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>