arm64: dts: mediatek: mt8195-demo: enable uart1

The UART1 is exposed on a header. Enable the uart1 node to be able to
use it.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Link: https://lore.kernel.org/r/20220426134106.242353-8-fparent@baylibre.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>