arm64: dts: mt7622: fix ram size for rfb1

Fix ram size to 512 megabytes and sort nodes in alphabetical order.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Acked-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>