ixgbe: Add X550EM support for SFP insertion interrupt

Add support for the SFP insertion interrupt on X550EM devices with
SFPs.

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>