drm: rcar-du: Fix the return value in case of error in 'rcar_du_crtc_set_crc_source()'

We return 0 unconditionally in 'rcar_du_crtc_set_crc_source()'.
However, 'ret' is set to some error codes if some function calls fail.

Return 'ret' instead to propagate the error code.

Fixes: 47a52d02 ("media: drm: rcar-du: Add support for CRC computation")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_crtc.c

@@ -1002,7 +1002,7 @@ static int rcar_du_crtc_set_crc_source(struct drm_crtc *crtc,
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
-	return 0;
+	return ret;
 }
 
 static const struct drm_crtc_funcs crtc_funcs_gen2 = {