igb: Implement support to power sfp cage and turn on I2C

Based on original patch from Aurélien Guillaume <footplus@gmail.com>
This patch adds support to turn on I2C, with sfp cage powered.

CC: Aurélien Guillaume <footplus@gmail.com>
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>