These were introduced in libdrm 2.4.68, commit
268ae7cae5afd76462c3ef14ed9021a2d40c2e57. Weston unconditionally
requires libdrm >= 2.4.95, so these fallback definitions are
unnecessary now.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>