drm/rockchip: Fix return type of cdn_dp_connector_mode_valid

The mode_valid field in drm_connector_helper_funcs is expected to be of
type:
enum drm_mode_status (* mode_valid) (struct drm_connector *connector,
				     struct drm_display_mode *mode);

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of cdn_dp_connector_mode_valid should be changed from
int to enum drm_mode_status.

Reported-by: Dan Carpenter <[email protected]>
Link: ClangBuiltLinux#1703
Cc: [email protected]
Signed-off-by: Nathan Huckleberry <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Signed-off-by: Heiko Stuebner <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: nhukc

drivers/gpu/drm/rockchip/cdn-dp-core.c

@@ -283,8 +283,9 @@ static int cdn_dp_connector_get_modes(struct drm_connector *connector)
 	return ret;
 }
 
-static int cdn_dp_connector_mode_valid(struct drm_connector *connector,
-				       struct drm_display_mode *mode)
+static enum drm_mode_status
+cdn_dp_connector_mode_valid(struct drm_connector *connector,
+			    struct drm_display_mode *mode)
 {
 	struct cdn_dp_device *dp = connector_to_dp(connector);
 	struct drm_display_info *display_info = &dp->connector.display_info;