bootconfig: Prohibit re-defining value on same key

In both styles, same key words are automatically merged when parsing it

at boot time. So you can append similar trees or key-values.

Note that a sub-key and a value can not co-exist under a parent key.

Same-key Values

---------------

It is prohibited that two or more values or arrays share a same-key.

For example,::

 foo = bar, baz

 foo = qux  # !ERROR! we can not re-define same key

Also, a sub-key and a value can not co-exist under a parent key.

For example, following config is NOT allowed.::

 foo = value1

static int __init xbc_parse_kv(char **k, char *v)

{

	struct xbc_node *prev_parent = last_parent;

	struct xbc_node *node, *child;

	struct xbc_node *child;

	char *next;

	int c, ret;

		return ret;

	child = xbc_node_get_child(last_parent);

	if (child && xbc_node_is_key(child))

	if (child) {

		if (xbc_node_is_key(child))

			return xbc_parse_error("Value is mixed with subkey", v);

		else

			return xbc_parse_error("Value is redefined", v);

	}

	c = __xbc_parse_value(&v, &next);

	if (c < 0)

		return c;

	node = xbc_add_sibling(v, XBC_VALUE);

	if (!node)

	if (!xbc_add_sibling(v, XBC_VALUE))

		return -ENOMEM;

	if (c == ',') {	/* Array */

# Same key value is not allowed

key {

	foo = value

	bar = value2

}

key.foo = value