libdrm: drmGetMinorNameForFD: Add FreeBSD variant

Use the FreeBSD variant function to obtain the minor name and the
device node.
Return the correct path based on where the node is (drm/ versus dri/).

Signed-off-by: Emmanuel Vadot <manu@FreeBSD.org>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>