drm/fsl-dcu: Fix return type of fsldcudrmconnectormode_valid()
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 v5.10.163 by commit f3d3f3564e8b28d39c540d30262dc34ab9e959d3. For more details please see the references link.