drm/amd/display: Enable DP YCbCr420 mode support for DCN10

[WHY]
In DCN10 when a panel with YCbCr420 capability is connected via
USB-C to HDMI active dongle, no YCbCr420 option is listed in
Radeon settings.

[HOW]
Enable DP YCbCr420 mode support for DCN10
Signed-off-by: Gary Li <gary.li@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c

@@ -798,7 +798,7 @@ static const struct encoder_feature_support link_enc_feature = {
 		.max_hdmi_deep_color = COLOR_DEPTH_121212,
 		.max_hdmi_pixel_clock = 600000,
 		.hdmi_ycbcr420_supported = true,
-		.dp_ycbcr420_supported = false,
+		.dp_ycbcr420_supported = true,
 		.flags.bits.IS_HBR2_CAPABLE = true,
 		.flags.bits.IS_HBR3_CAPABLE = true,
 		.flags.bits.IS_TPS3_CAPABLE = true,