xwayland: use drmGetNodeTypeFromFd for checking if a node is a render one

Major/minor numbers are a.. major (ha) source of pain in FreeBSD porting.
In this case, Xwayland was thinking that /dev/dri/card0 is already a render node,
because the st_rdev on FreeBSD was passing the Linux-style check,
and because of the assumption, acceleration would fail because
various ioctls like AMDGPU_INFO would be denied on the non-render node.

Switch to libdrm's function that already works correctly on all platforms.

Signed-off-by: Greg V <greg@unrelenting.technology>
Reviewed-by: Emmanuel Vadot <manu@FreeBSD.org>
4 jobs for xw-fbsd in 4 minutes and 17 seconds (queued for 1 second)