i40e: declare rather than initialize int object

'err' would be overwritten immediately, so we should declare it only
rather than initialize it to zero.

Signed-off-by: Jean Sacren <sakiwit@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>