igb: rename nvm ops

All of the nvm ops have the tag _nvm added to the end which is redundant
since all of the calls to the ops have to go through the nvm ops struct
anyway.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>