fs/9p: remove sparse warning in vfs_inode

make v9fs_dentry_from_dir_inode static
Signed-off-by: NEric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_inode.c

@@ -260,7 +260,7 @@ static gid_t v9fs_get_fsgid_for_create(struct inode *dir_inode)
  *
  */
 
-struct dentry *v9fs_dentry_from_dir_inode(struct inode *inode)
+static struct dentry *v9fs_dentry_from_dir_inode(struct inode *inode)
 {
 	struct dentry *dentry;