arm64: dts: mt8173: fix mdp aliases property name

Fix warning:
Warning (alias_paths): /aliases: aliases property name must include only lowercase and '-'

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Link: https://lore.kernel.org/r/20200414030815.192104-1-hsinyi@chromium.org


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