arm64: dts: mediatek: mt7622-rfb1: remove wrong gpio-keys property

gpio-keys (regular, not polling) does not use "poll-interval" property.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220617232124.7022-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>