ixgbe: Check for setup_internal_link method

Only call the internal_setup_link method when it is provided. This
check is required for newer version parts.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Darin Miller <darin.j.miller@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>