The size of device tree node secmon (bl31_secmon_reserved) was
incorrect. It should be increased to 2MiB (0x200000).

The origin setting will cause some abnormal behavior due to
trusted-firmware-a and related firmware didn't load correctly.
The incorrect behavior may vary because of different software stacks.
For example, it will cause build error in some Yocto project because
it will check if there was enough memory to load trusted-firmware-a
to the reserved memory.

When mt8195-demo.dts sent to the upstream, at that time the size of
BL31 was small. Because supported functions and modules in BL31 are
basic sets when the board was under early development stage.

Now BL31 includes more firmwares of coprocessors and maturer functions
so the size has grown bigger in real applications. According to the value
reported by customers, we think reserved 2MiB for BL31 might be enough
for maybe the following 2 or 3 years.

Cc: stable@vger.kernel.org      # v5.19
Fixes: 6147314a ("arm64: dts: mediatek: Add device-tree for MT8195 Demo board")
Signed-off-by: Macpaul Lin <macpaul.lin@mediatek.com>
Reviewed-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221111095540.28881-1-macpaul.lin@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>