drm/msm/dp: program config ctrl for YUV420 over DP

Change relevant DP controller related programming for YUV420 cases.
Program the configuration control register to indicate YUV420.

Changes in v2:
	- Create a new patch only for configuration control programming

Signed-off-by: Paloma Arellano <quic_parellan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/579615/
Link: https://lore.kernel.org/r/20240222194025.25329-11-quic_parellan@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Author: Paloma Arellano

drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -142,6 +142,9 @@ static void dp_ctrl_config_ctrl(struct dp_ctrl_private *ctrl)
 	/* Default-> LSCLK DIV: 1/4 LCLK  */
 	config |= (2 << DP_CONFIGURATION_CTRL_LSCLK_DIV_SHIFT);
 
+	if (ctrl->panel->dp_mode.out_fmt_is_yuv_420)
+		config |= DP_CONFIGURATION_CTRL_RGB_YUV; /* YUV420 */
+
 	/* Scrambler reset enable */
 	if (drm_dp_alternate_scrambler_reset_cap(dpcd))
 		config |= DP_CONFIGURATION_CTRL_ASSR;