i40iw: Report correct firmware version

The driver uses a hard-coded value for FW version and reports an
inconsistent FW version between ibv_devinfo and
/sys/class/infiniband/i40iw/fw_ver.

Retrieve the FW version via a Control QP (CQP) operation and report it
consistently across sysfs and query device.

Fixes: d3749841

 ("i40iw: add files for iwarp interface")
Link: https://lore.kernel.org/r/20200313214406.2159-1-shiraz.saleem@intel.com
Reported-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Sindhu, Devale <sindhu.devale@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>