dt-bindings: pinctrl: brcm,ns-pinmux: drop unneeded CRU from example

There is no need to include CRU in example of this binding. It wasn't
complete / correct anyway. The proper binding can be find in the
mfd/brcm,cru.yaml .

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211008205938.29925-2-zajec5@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>