drm/bridge: Prioritize supported_formats over ycbcr_420_allowed

Bridges having DRM_BRIDGE_OP_HDMI set in their ->ops are supposed to
rely on the ->supported_formats bitmask to advertise the permitted
colorspaces, including HDMI_COLORSPACE_YUV420.

However, a new flag ->ycbcr_420_allowed has been recently introduced,
which brings the necessity to require redundant and potentially
inconsistent information to be provided on HDMI bridges initialization.

Adjust ->ycbcr_420_allowed for HDMI bridges according to
->supported_formats, right before adding them to the global bridge list.
This keeps the initialization process straightforward and unambiguous,
thereby preventing any further confusion.

Fixes: 3ced1c6 ("drm/display: bridge_connector: handle ycbcr_420_allowed")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241224-bridge-conn-fmt-prio-v4-1-a9ceb5671379@collabora.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Author: cristicc

drivers/gpu/drm/drm_bridge.c

@@ -207,6 +207,10 @@ void drm_bridge_add(struct drm_bridge *bridge)
 {
 	mutex_init(&bridge->hpd_mutex);
 
+	if (bridge->ops & DRM_BRIDGE_OP_HDMI)
+		bridge->ycbcr_420_allowed = !!(bridge->supported_formats &
+					       BIT(HDMI_COLORSPACE_YUV420));
+
 	mutex_lock(&bridge_lock);
 	list_add_tail(&bridge->list, &bridge_list);
 	mutex_unlock(&bridge_lock);