cnic: Fix locking in init/exit calls.

The slow path ulp_init and ulp_exit calls to the bnx2i driver
are sleepable calls and therefore should not be protected using
rcu_read_lock.  Fix it by using mutex and refcount during these
calls.  cnic_unregister_driver() will now wait for the refcount
to go to zero before completing the call.

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/cnic_if.h b/drivers/net/cnic_if.h
index d1bce27..a492357 100644
--- a/drivers/net/cnic_if.h
+++ b/drivers/net/cnic_if.h
@@ -290,6 +290,7 @@
 	void (*iscsi_nl_send_msg)(struct cnic_dev *dev, u32 msg_type,
 				  char *data, u16 data_size);
 	struct module *owner;
+	atomic_t ref_count;
 };
 
 extern int cnic_register_driver(int ulp_type, struct cnic_ulp_ops *ulp_ops);