drm/omap: fix NULL but dereferenced coccicheck error
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 v5.18.3 by commit 08d9a75eab594ca508a440db7c73064498d26687, it was introduced in version v5.17 by commit e02b5cc9e898ad6f223a69df63397beae60390ff. For more details please see the references link.