cnic: Fix crash during bnx2x MTU change.

cnic_service_bnx2x() irq handler can be called during chip reset from
MTU change.  Need to check that the cnic's device state is up before
handling the irq.
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/cnic.c

@@ -2334,13 +2334,13 @@ static int cnic_service_bnx2x(void *data, void *status_blk)
 	struct cnic_local *cp = dev->cnic_priv;
 	u16 prod = cp->kcq_prod_idx & MAX_KCQ_IDX;
 
-	prefetch(cp->status_blk.bnx2x);
-	prefetch(&cp->kcq[KCQ_PG(prod)][KCQ_IDX(prod)]);
+	if (likely(test_bit(CNIC_F_CNIC_UP, &dev->flags))) {
+		prefetch(cp->status_blk.bnx2x);
+		prefetch(&cp->kcq[KCQ_PG(prod)][KCQ_IDX(prod)]);
 
-	if (likely(test_bit(CNIC_F_CNIC_UP, &dev->flags)))
 		tasklet_schedule(&cp->cnic_irq_task);
-
-	cnic_chk_pkt_rings(cp);
+		cnic_chk_pkt_rings(cp);
+	}
 
 	return 0;
 }