[src/trunk]: src/sys/external/bsd/drm2/include More Linux header stubs.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d0a2f7010948
branches:  trunk
changeset: 1027782:d0a2f7010948
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 00:30:01 2021 +0000

description:
More Linux header stubs.

Let's just use empty header files until we actually populate these.
Save a bit of disk space...