procfs: fix a vfsmount longterm reference leak

kern_mount() doesn't pair with plain mntput()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, struct nameidata *nd)
{
	if (!proc_lookup(dir, dentry, nd)) {
		return NULL;
	}
	
	return proc_pid_lookup(dir, dentry, nd);
}

static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, struct nameidata *nd)
{
	if (!proc_lookup(dir, dentry, nd)) {
		return NULL;
	}
	
	return proc_pid_lookup(dir, dentry, nd);
}
