net/mlx5: fix memory regions release deadlock

net/mlx5: fix memory regions release deadlock

The mpx5 PMD maintains the list of devices for those the memory
operation callback routines must be invoked to keep the device MRs (MR
is the entity backing the hardware DMA transactions) consistent with the
mapped memory.
Each device context in the list is protected with dedicated lock on per
device basis, which might be taken inside the callback routine.

When device is closing the PMD frees all MRs by calling
mlx5_mr_release(), that might call rte_free() under the taken device
lock.  If this rte_free call triggers the entire memory segment freeing
it, in its turn, invokes the callback routine and attempt to take the
lock inside this one causes the deadlock.

The patch proposes the remove the device from the callback list first
and then call mlx5_mr_release() and free the remaining device MRs
explicitly.

Fixes: 0e3d0525b2f2 ("net/mlx5: fix memory event callback list")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>