arm64: dts: mediatek: mt8186: Merge Voltorb device trees

arm64: dts: mediatek: mt8186: Merge Voltorb device trees

There are only two different SKUs of Voltorb, and the only difference
between them is whether a touchscreen is present or not. This can be
detected by a simple I2C transfer to the address, instead of having
separate device trees.

Merge the two device trees together and simplify the compatible string
list. The dtsi is still kept separate since there is an incoming device
that shares the same design, but with slightly difference components.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20250617082004.1653492-6-wenst@chromium.org
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>