igb: remove unused switch statement from igb_set_wol

There is a switch statement in igb_set_wol that defaults to break and
doesn't actually do anything.  As such it should be removed.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>