i40iw: Avoid writing to freed memory

i40iw: Avoid writing to freed memory

commit 433c58139f6a7d59824aadd23d6c9cac1d4e6100 upstream.

iwpbl->iwmr points to the structure that contains iwpbl,
which is iwmr. Setting this to NULL would result in
writing to freed memory. So just free iwmr, and return.

Fixes: d37498417947 ("i40iw: add files for iwarp interface")
Reported-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>