arm64: dts: mediatek: mt8195-demo: fix the memory size to 8GB

commit 25389c03 upstream.

The onboard dram of mt8195-demo board is 8GB.

Cc: stable@vger.kernel.org      # 6.1, 6.4, 6.5
Fixes: 6147314a

 ("arm64: dts: mediatek: Add device-tree for MT8195 Demo board")
Signed-off-by: Macpaul Lin <macpaul.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230905034511.11232-1-macpaul.lin@mediatek.com
Link: https://lore.kernel.org/r/20231003-mediatek-fixes-v6-7-v1-2-dad7cd62a8ff@collabora.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>