ixgbe: fix issue with sfp events with new X550 devices

Add checks for systems that don't have SFP's to avoid incorrectly
acting on interrupts that are falsely interpreted as SFP events.
We do this by updating the ixgbe_is_sfp to be aware of the
new X550 devices.  This also includes a modified check generating
the EICR mask to be more forward-looking.

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>