net/can/mscan: fix function annotations

- use extern where apropriate
- don't export symbols

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/can/mscan/mscan.h b/drivers/net/can/mscan/mscan.h
index 76a8abf..2018000 100644
--- a/drivers/net/can/mscan/mscan.h
+++ b/drivers/net/can/mscan/mscan.h
@@ -279,7 +279,7 @@
 	struct napi_struct napi;
 };
 
-struct net_device *alloc_mscandev(void);
+extern struct net_device *alloc_mscandev(void);
 /*
  * clock_src:
  *	1 = The MSCAN clock source is the onchip Bus Clock.