connector: make callback argument type explicit

The connector documentation states that the argument to the callback
function is always a pointer to a struct cn_msg, but rather than encode it
in the API itself, it uses a void pointer everywhere.  This doesn't make
much sense to encode the pointer in documentation as it prevents proper C
type checking from occurring and can easily allow people to use the wrong
pointer type.  So convert the argument type to an explicit struct cn_msg
pointer.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index c5afc98..85e5dc0 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -202,9 +202,8 @@
  * cn_proc_mcast_ctl
  * @data: message sent from userspace via the connector
  */
-static void cn_proc_mcast_ctl(void *data)
+static void cn_proc_mcast_ctl(struct cn_msg *msg)
 {
-	struct cn_msg *msg = data;
 	enum proc_cn_mcast_op *mc_op = NULL;
 	int err = 0;