egl/wayland: libdrm is a hard requirement, treat it as such
Prompt at configure time if it's missing otherwise we'll fail later on in the build. Remove ambiguous HAVE_LIBDRM guard. Cc: 10.6 <mesa-stable@lists.freedesktop.org> Signed-off-by:Emil Velikov <emil.l.velikov@gmail.com> (cherry picked from commit fa109d02)