arm64: dts: meson: libretech-cc: switch eMMC to 1.8v

While some 3.3v eMMC 4.0 are available from libretech, Only the 1.8v 5.0
modules are recommended and supported for the aml-s905x-cc.

the 1.8v is provided by LDOs on the eMMC card, from vcc 3.3v

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