drm.4: Update a bit to reflect the current state of affairs.

While here, remove an obsolete MLINK, and add some more MLINKS to cover
module names too.

Based on a patch by ftigeot, with additional input by him.
Disable making i915kms compilable into the kernel.

Right now, on systems with supported cards, it would cause the screen
go black before Xorg is started.

In-discussion-with: ftigeot