ixgbe: Restore ESDP settings after MAC reset

The I2C mux control relies on the SDP setting in the ESDP register
so it is necessary to restore the value after a MAC reset.  Combine
all this functionality in to a support function.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>