drm/amd/display: fix YCbCr420 deep color mode not supported

Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.c

@@ -858,6 +858,8 @@ bool dcn_validate_bandwidth(
 				- pipe->stream->public.timing.v_front_porch;
 		v->vactive[input_idx] = pipe->stream->public.timing.v_addressable;
 		v->pixel_clock[input_idx] = pipe->stream->public.timing.pix_clk_khz / 1000.0f;
+		if (pipe->stream->public.timing.pixel_encoding == PIXEL_ENCODING_YCBCR420)
+			v->pixel_clock[input_idx] /= 2;
 
 
 		if (!pipe->surface){