dt-bindings: net: ti: k3-am654-cpsw-nuss: Drop pinmux header

Drop the pinmux header reference as it is not used. Examples should
just show the node definition.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230315155228.1566883-2-nm@ti.com


Signed-off-by: Nishanth Menon <nm@ti.com>