ARM: dts: meson8: remove gpio offset

Remove pin offset on the AO controller. meson pinctrl no longer has
this quirk

Tested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>