ixgbe: Resolve "initialized field overwritten" warnings

Resolve warnings resulting from redundant initialization of the
get_bus_info field in the mac_ops_X550* structures.

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>