drm/amd/display: PIP overlay corruption

[Why]
When moving mouse onto or off of pip plane,
screen would flash briefly due to garbage negative
pos values being programmed for cursor.
Also, text flashes due to PIP flips taking too long.

[How]
When negative pos value seen, default to 0 and adjust by modifying cursor hotspot.
For flip issue, only do post update when optimize required vs all the time.

Signed-off-by: Murton Liu <murton.liu@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Sivapiriyan Kumarasamy <Sivapiriyan.Kumarasamy@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>