Take the dbgmgr lock and unregister before destroying the debug manager.
Do this before destroying the queues.

v2: Correct locking order in kfd_ioctl_dbg_register to ake sure the
process mutex and dbgmgr mutex are always taken in the same order.
Signed-off-by: Yair Shachar <yair.shachar@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>