iavf: fix a typo

This trivial patch fixes a typo in iavf.h.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>