GSD-2023-1000586 drm/meson: Fix return type of meson_encoder_cvbs_mode_valid()

drm/meson: Fix return type of mesonencodercvbsmodevalid 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 v6.0.16 by commit...