dt-bindings: pinctrl: aspeed: Drop referenced nodes in examples

The additional nodes in the example referenced from the pinctrl node
'aspeed,external-nodes' properties are either incorrect (aspeed,ast2500-lpc)
or not documented with a schema (aspeed,ast2500-gfx). There's no need to
show these nodes as part of the pinctrl example, so just remove them.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220422192139.2592632-1-robh@kernel.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>