drm/dp: Fix off-by-one in register cache size
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 v5.15.33 by commit e912d697400c5f4bc8c1c8090416dad6c59cb28c, it was introduced in version v5.12 by commit e2e16da398d9149ede0162a55f44537582aed2e7. For more details please see the references link.