pinctrl: dt-binding: fix generic pinmux/pinconf examples

pinconf_generic_dt_node_to_map() scans only subnodes of the pinctrl-0 pahndle,
not the referenced node itself. Change the example nodes to match.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>