Allow gpio-line-names property for the gpio subnodes.

Fixes: 94df03a4 ("dt-bindings: pinctrl: Convert Amlogic Meson pinctrl binding")
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230707-topic-amlogic-upstream-pinctrl-fix-bindings-v2-1-2160060446d7@linaro.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>