fsnotify: put inode specific fields in an fsnotify_mark in a union

The addition of marks on vfs mounts will be simplified if the inode
specific parts of a mark and the vfsmnt specific parts of a mark are
actually in a union so naming can be easy.  This patch just implements the
inode struct and the union.

Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 9eddafa..fc3a9dc 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -70,8 +70,8 @@
 	if (old_mask == new_mask)
 		return;
 
-	if (entry->inode)
-		fsnotify_recalc_inode_mask(entry->inode);
+	if (entry->i.inode)
+		fsnotify_recalc_inode_mask(entry->i.inode);
 }
 
 /*