xf86drm: implement an OpenBSD specific drmGetDevice2
DRI devices on OpenBSD are not in their own directory. They reside in
/dev with a large number of statically generated /dev nodes.
Avoid stat'ing all of /dev on OpenBSD by implementing this custom path.
v2:
- use drmGetMinorType to get node type
- adapt to drmProcessPciDevice changes
- verify drmParseSubsystemType type is PCI
- add a comment describing why this was added
Signed-off-by: Jonathan Gray <jsg@jsg.id.au>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>