i40iw: Change mem_resources pointer to a u8

iwdev->mem_resources is incorrectly defined as an unsigned
long instead of u8. As a result, the offset into the dynamic
allocated structures in i40iw_initialize_hw_resources() is
incorrectly calculated and would lead to writing of memory
regions outside of the allocated buffer.

Fixes: 8e06af71 ("i40iw: add main, hdr, status")

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>