make proc_ns_operations work with struct ns_common * instead of void *

We can do that now.  And kill ->inum(), while we are at it - all instances
are identical.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 3c1e8d3..531029a 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -154,7 +154,7 @@
 	return container_of(ns, struct ipc_namespace, ns);
 }
 
-static void *ipcns_get(struct task_struct *task)
+static struct ns_common *ipcns_get(struct task_struct *task)
 {
 	struct ipc_namespace *ns = NULL;
 	struct nsproxy *nsproxy;
@@ -168,12 +168,12 @@
 	return ns ? &ns->ns : NULL;
 }
 
-static void ipcns_put(void *ns)
+static void ipcns_put(struct ns_common *ns)
 {
 	return put_ipc_ns(to_ipc_ns(ns));
 }
 
-static int ipcns_install(struct nsproxy *nsproxy, void *new)
+static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 {
 	struct ipc_namespace *ns = to_ipc_ns(new);
 	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
@@ -187,16 +187,10 @@
 	return 0;
 }
 
-static unsigned int ipcns_inum(void *vp)
-{
-	return ((struct ns_common *)vp)->inum;
-}
-
 const struct proc_ns_operations ipcns_operations = {
 	.name		= "ipc",
 	.type		= CLONE_NEWIPC,
 	.get		= ipcns_get,
 	.put		= ipcns_put,
 	.install	= ipcns_install,
-	.inum		= ipcns_inum,
 };