drm/amd/display: Add 4 to 1 MPC split support

drm/amd/display: Add 4 to 1 MPC split support

[Why]
Want to make use of detile buffer of all 4 pipes to maximize amount of
data stored to hide certain memory latency cases.

[How]
In case of 1 plane and 1 stream, program 4 pipes to each retrieve 1/4 of
plane later mixed together by the MPCs. Added support for transition
from 4 to 1 MPC to 2 to 1 MPC or no pipe split case and vice versa.
Currently, only enabled if debug flag is set.

Signed-off-by: Isabel Zhang <isabel.zhang@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>