igb: Add i2c interface to igb.

Some of our adapters have sensors on them accessible via i2c and a private
interface.  This patch implements the kernel interface for i2c to those sensors.
Subsequent patches will provide functions to export that data.

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/ethernet/intel/igb/e1000_hw.h b/drivers/net/ethernet/intel/igb/e1000_hw.h
index c2a51dc..75312ba 100644
--- a/drivers/net/ethernet/intel/igb/e1000_hw.h
+++ b/drivers/net/ethernet/intel/igb/e1000_hw.h
@@ -342,6 +342,8 @@
 	s32  (*set_d0_lplu_state)(struct e1000_hw *, bool);
 	s32  (*set_d3_lplu_state)(struct e1000_hw *, bool);
 	s32  (*write_reg)(struct e1000_hw *, u32, u16);
+	s32 (*read_i2c_byte)(struct e1000_hw *, u8, u8, u8 *);
+	s32 (*write_i2c_byte)(struct e1000_hw *, u8, u8, u8);
 };
 
 struct e1000_nvm_operations {