arm64: dts: mediatek: mt8195-demo: configure to 8GB DRAM
Currently there are only 2GB DRAM configured on the i1200-demo(MT8395 P1V5 & P1V6) board.
But physically, the board have 8GB DRAM available.
Fix AIOT-1226
Signed-off-by: Pablo Sun pablo.sun@mediatek.com