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 v5.15.86 by commit f3c14b99f33a7fe6a8015a2086146928772947bf. For more details please see the references link.