i40e: clean up local variable initialization

i40e: clean up local variable initialization

Orabug: 22342532

In both i40e_calc_nvm_checksum() and i40e_update_nvm_checksum(), the
local variables designated by 'ret_code' are overwritten immediately. As
such, they should merely be declared.

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>
(cherry picked from commit 0e5229c6c576969bf8f89f8ca74fa7ea355b434e)
Signed-off-by: Brian Maly <brian.maly@oracle.com>