RDMA/mlx5: Issue FW command to destroy SRQ on reentry

RDMA/mlx5: Issue FW command to destroy SRQ on reentry

The HW release can fail and leave the system in limbo state, where SRQ is
removed from the table, but can't be destroyed later.  In every reentry,
the initial xa_erase_irq() check will fail.

Rewrite the erase logic to keep index, but don't store the entry
itself. By doing it, we can safely reinsert entry back in the case of
destroy failure.

Link: https://lore.kernel.org/r/20200907120921.476363-4-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>