dri1: Don't bother asking the loader about drmGetLibVersion

dri1: Don't bother asking the loader about drmGetLibVersion

This was added for DRM_IOCTL_SET_VERSION support, which has been around
for over ten years now. Since we require ≥2.3.0 in configure.ac this
would really only protect you if you managed to build against a modern
libdrm but run against one that's more than 7½ years old, which, doctor
it hurts when I do this.

Archaeology: http://cgit.freedesktop.org/~ajax/dri/commit/xc/programs/Xserver/GL/dri/dri.c?id=77d62efca033dced96ab7998b7c62a4e2df907d5
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Keith Packard <keithp@keithp.com>