473e0ecbb4
[Why] Alpha could be improperly applied (only affecting half the frame) for some source pixel formats. [How] Change how alpha is enabled in MPC/DPP LB and change the bottom plane blend mode in MPC. Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com> Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com> Acked-by: Leo Li <sunpeng.li@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>