Now that the SRCU stuff has been removed the entire MR destroy logic can
be made a lot simpler. Currently there are many different ways to destroy a
MR and it makes it really hard to do this task correctly. Route all
destruction through mlx5_ib_dereg_mr() and make it work for all
situations.
Since it turns out all the different MR types do basically the same thing
this removes a lot of knowledge of MR internals from ODP and leaves ODP
just exporting an operation to clean up children.
This fixes a few weird corner cases bugs and firmly uses the correct
ordering of the MR destruction:
- Stop parallel access to the mkey via the ODP xarray
- Stop DMA
- Release the umem
- Clean up ODP children
- Free/Recycle the MR