RDMA/i40iw: Avoid panic when objects are being created and destroyed

A panic occurs when there is a newly-registered element on the QP/CQ MR
list waiting to be attached, but a different MR is deregistered. The
current code only checks for whether the list is empty, not whether the
element being deregistered is actually on the list.

Fix the panic by adding a boolean to track if the object is on the list.

Fixes: d3749841 ("i40iw: add files for iwarp interface")
Signed-off-by: Andrew Boyer <andrew.boyer@dell.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>