arm64: dts: amlogic: meson-gx-libretech-pc: fix update button name

Fixes:
 adc-keys: 'update-button' does not match any of the regexes: '^button-', 'pinctrl-[0-9]+'

Link: https://lore.kernel.org/r/20230124-b4-amlogic-bindings-fixups-v1-10-44351528957e@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>