ARM: dts: amlogic: meson6: remove support for ATV1200 board

ARM: dts: amlogic: meson6: remove support for ATV1200 board

The meson6 atv1200 has a lot of dtbs check errors, but since
no active contributor have any boards with Meson6 SoC, plus
no upstream GPIO, pinctrl, clock, MMC... for that SoC either,
let's start decommissioning Meson6 support by removing the Device
Tree files first then remove the MACH_MESON6 in a second time.

If someone is interested in Meson6 support they should bring it back
along with a few more patches for upstream support of further
peripherals.

Suggested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20240916-topic-amlogic-arm32-upstream-bindings-fixes-v2-4-0b20ed4f0571@linaro.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>