drm/amd/display: update dio for two pixel per container case

[why]
Processing rate of the DP encoder, must be programmed to be the same as
DIG_FIFO_OUTPUT_ PROCESSING_MODE in DP mode
0: 1 pixel per cycle
1: 2 pixel per cycle

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>