fs/namespace: correct/improve kernel-doc notation

Fix kernel-doc warnings in fs/namespace.c:

./fs/namespace.c:1379: warning: Function parameter or member 'm' not described in 'may_umount_tree'
./fs/namespace.c:1379: warning: Excess function parameter 'mnt' description in 'may_umount_tree'
./fs/namespace.c:1950: warning: Function parameter or member 'path' not described in 'clone_private_mount'

Also convert path_is_mountpoint() comments to kernel-doc.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Allegedly-acked-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20210318025227.4162-1-rdunlap@infradead.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

fs/namespace.c

@@ -1242,8 +1242,9 @@ struct vfsmount *mntget(struct vfsmount *mnt)
 }
 EXPORT_SYMBOL(mntget);
 
-/* path_is_mountpoint() - Check if path is a mount in the current
- *                          namespace.
+/**
+ * path_is_mountpoint() - Check if path is a mount in the current namespace.
+ * @path: path to check
  *
  *  d_mountpoint() can only be used reliably to establish if a dentry is
  *  not mounted in any namespace and that common case is handled inline.
@@ -1369,7 +1370,7 @@ void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
 
 /**
  * may_umount_tree - check if a mount tree is busy
- * @mnt: root of mount tree
+ * @m: root of mount tree
  *
  * This is called to check if a tree of mounts has any
  * open files, pwds, chroots or sub mounts that are
@@ -1939,10 +1940,11 @@ void drop_collected_mounts(struct vfsmount *mnt)
 
 /**
  * clone_private_mount - create a private clone of a path
+ * @path: path to clone
  *
- * This creates a new vfsmount, which will be the clone of @path.  The new will
- * not be attached anywhere in the namespace and will be private (i.e. changes
- * to the originating mount won't be propagated into this).
+ * This creates a new vfsmount, which will be the clone of @path.  The new mount
+ * will not be attached anywhere in the namespace and will be private (i.e.
+ * changes to the originating mount won't be propagated into this).
  *
  * Release with mntput().
  */