configure.ac: bump LIBDRM_RADEON requirement to 2.4.71

Such that we can remove all the local fall-back definitions and use the
official UABI ones.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
1 file changed