GSD-2023-1001545 drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()

drm/fsl-dcu: Fix return type of fsldcudrmconnectormodevalid This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v4.9.337 by commit...