iavf: change iavf_status_code to iavf_status

Instead of typedefing the enum iavf_status_code with iavf_status,
just shorten the enum itself and get rid of typedef.

Signed-off-by: Sergey Nemov <sergey.nemov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>