arm64: dts: meson-gxm-khadas-vim2: use gpio-fan matrix instead of an array

No functional changes.

Adjust to comply with dt-schema requirements
and make it possible to validate values.

Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20230126193732.69699-1-david@ixit.cz


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