i40e: Change BUG_ON to WARN_ON in service event complete

BugLink: http://bugs.launchpad.net/bugs/1536474

There's no need to kill the thread and eventually the kernel in this
case.  In fact, the remainder of the code won't hurt anything anyway,
so just complain that we're here and move along.

Prompted by a recent Linus diatribe.

Change-ID: Iec020d8bcfedffc1cd2553cc6905fd915bb3e670
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit b875f99b)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -5738,7 +5738,7 @@ static void i40e_handle_lan_overflow_event(struct i40e_pf *pf,
  **/
 static void i40e_service_event_complete(struct i40e_pf *pf)
 {
-	BUG_ON(!test_bit(__I40E_SERVICE_SCHED, &pf->state));
+	WARN_ON(!test_bit(__I40E_SERVICE_SCHED, &pf->state));
 
 	/* flush memory to make sure state is correct before next watchog */
 	smp_mb__before_atomic();