I have patches to add locking to mlx(4) and mark it MPSAFE. The patches are
from HEAD but should apply to 8 or 9. If you test it on 8 or 9 please enable
INVARIANTS for at least the initial testing. Thanks.
Given that this is a driver for older hardware, if no one is able to test
these patches, then I will remove the driver from HEAD after committing these