igb: Update NVM functions to work with i350 devices

This patch adds functions and functions pointers to accommodate
differences between NVM interfaces and options for i350 devices,
82580 devices and the rest.

Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/igb/e1000_nvm.h b/drivers/net/igb/e1000_nvm.h
index 29c956a..7f43564 100644
--- a/drivers/net/igb/e1000_nvm.h
+++ b/drivers/net/igb/e1000_nvm.h
@@ -35,6 +35,7 @@
 s32  igb_read_part_string(struct e1000_hw *hw, u8 *part_num,
                           u32 part_num_size);
 s32  igb_read_nvm_eerd(struct e1000_hw *hw, u16 offset, u16 words, u16 *data);
+s32  igb_read_nvm_spi(struct e1000_hw *hw, u16 offset, u16 words, u16 *data);
 s32  igb_write_nvm_spi(struct e1000_hw *hw, u16 offset, u16 words, u16 *data);
 s32  igb_validate_nvm_checksum(struct e1000_hw *hw);
 s32  igb_update_nvm_checksum(struct e1000_hw *hw);