drm: Use size_t type for len variable in drm_copy_field()
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 v4.19.262 by commit 54e5fbda9bac666fcb746f186481cc15a8bbb91d. For more details please see the references link.