e1000e: Do not write lsc to ics in msi-x mode

In msi-x mode, there is no handler for the lsc interrupt so there is no
point in writing that to ics now that we always assume Other interrupts
are caused by lsc.

Reviewed-by: Jasna Hodzic <jhodzic@ucdavis.edu>
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>