snap: handle registration error and compile warning

If this module can't load, it is almost certainly because something else
is already bound to that SAP. So in that case, return the same error code
as other SAP usage, and fail the module load.

Also fixes a compiler warning about printk of non const.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Acked-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/802/psnap.c

@@ -95,15 +95,16 @@ static int snap_request(struct datalink_proto *dl,
 EXPORT_SYMBOL(register_snap_client);
 EXPORT_SYMBOL(unregister_snap_client);
 
-static char snap_err_msg[] __initdata =
+static const char snap_err_msg[] __initconst =
 	KERN_CRIT "SNAP - unable to register with 802.2\n";
 
 static int __init snap_init(void)
 {
 	snap_sap = llc_sap_open(0xAA, snap_rcv);
-
-	if (!snap_sap)
+	if (!snap_sap) {
 		printk(snap_err_msg);
+		return -EBUSY;
+	}
 
 	return 0;
 }