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.
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>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>