i40e: fix incorrect variable assignment

Fix incorrect variable assignment.
Based on line 1511: aq_ret = I40_ERR_PARAM; the correct variable to be
used in this instance is aq_ret instead of ret. Also, variable ret is
updated at line 1602 just before return, so assigning a value to this
variable in this code block is useless.

Addresses-Coverity-ID: 1397693
Signed-off-by: Gustavo A R Silva <garsilva@embeddedor.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>