drm/amd/display: update add plane to context logic with a new algorithm

[why]
Preivous algorithm for finding an optimal idle pipe for a new plane was
implemented to handle dynamic pipe allocation when MPO plane moves
from one ODM slice to the other. Now pipe allocation is more static so
it no longer depends on the MPO plane's position. We are simplifying
our logic and remove unnecessary handling in our code.

[how]
Apply a new simplified version of pipe resource allocation logic to reduce
unnecessary flip delay caused by swapping secondary dpp pipe to other
MPC blending tree.

Reviewed-by: Jun Lei <jun.lei@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>