drm/amd/display: Subsample mode suboptimal for YCbCr4:2:2

[Why&How]
Driver defaults to 1-tap subsample mode for 4:2:2.
DCE11.2 added 3-tap. The policy is:
DCE8-DCE11 - change to 2-tap, it's better than 1-tap.
DCE11.2+ - use 3-tap

Note that 4:2:0 was added in DCE11.2 and already uses 3-tap always.
Note 2 is that DCE not covered on Linux, only DCN+
Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_opp.c

@@ -168,7 +168,10 @@ static void opp1_set_pixel_encoding(
 		REG_UPDATE(FMT_CONTROL, FMT_PIXEL_ENCODING, 0);
 		break;
 	case PIXEL_ENCODING_YCBCR422:
-		REG_UPDATE(FMT_CONTROL, FMT_PIXEL_ENCODING, 1);
+		REG_UPDATE_3(FMT_CONTROL,
+				FMT_PIXEL_ENCODING, 1,
+				FMT_SUBSAMPLING_MODE, 2,
+				FMT_CBCR_BIT_REDUCTION_BYPASS, 0);
 		break;
 	case PIXEL_ENCODING_YCBCR420:
 		REG_UPDATE(FMT_CONTROL, FMT_PIXEL_ENCODING, 2);

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_opp.h

@@ -116,6 +116,8 @@
 	type FMT_RAND_G_SEED; \
 	type FMT_RAND_B_SEED; \
 	type FMT_PIXEL_ENCODING; \
+	type FMT_SUBSAMPLING_MODE; \
+	type FMT_CBCR_BIT_REDUCTION_BYPASS; \
 	type FMT_CLAMP_DATA_EN; \
 	type FMT_CLAMP_COLOR_FORMAT; \
 	type FMT_DYNAMIC_EXP_EN; \