ixgbe: Enable bit-banging mode on X550

Set the bit banging mode in the hardware when performing bit banging
I2C operations on X550. Also control the output enable on both the
clock and data lines.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>