drm: Use sizet type for len variable in drmcopy_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 v5.10.150 by commit e7d701800365d2dd3ef2252497dcaed9a2d2fada. For more details please see the references link.