bnx2: Use mutex on slow path cnic calls.

The slow path calls to the cnic driver are sleepable calls so we
cannot use rcu_read_lock().  Use mutex for these slow path calls
instead.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bnx2.h b/drivers/net/bnx2.h
index f1edfaa..a4f12fd 100644
--- a/drivers/net/bnx2.h
+++ b/drivers/net/bnx2.h
@@ -6902,6 +6902,7 @@
 	u32			idle_chk_status_idx;
 
 #ifdef BCM_CNIC
+	struct mutex		cnic_lock;
 	struct cnic_eth_dev	cnic_eth_dev;
 #endif