ixgbe: add SFP+ driver support

This patch adds support for SFP+ PHY in the following device ID's (10DB,
10F1, 10E1).  These SFP+ PHY's are accessed via an I2C interface so the
patch also includes functions to support this.

Another feature of note is that the PHY is pluggable and some
rearchitecting was needed to support this.

Signed-off-by: Donald Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>