The drm feature solves the problem of creating a common entry
point for adding kernel drm modules for different package lists.
The need for allocation into a separate feature arose from one
parties to the need to make a switch between free and proprietary
NVIDIA driver, on the other, because of the need to add only drm
modules kernels for purposes such as use/stage2/kms and use/plymouth.

Also no more switch needed for RADEON, as only the free video driver
remains.