arm64: dts: mediatek: mt8192-asurada: Couple VGPU and VSRAM_OTHER regulators

Add coupling for these regulators, as VSRAM_OTHER is used to power the
GPU SRAM, and they have a strict voltage output relation to satisfy in
order to ensure GPU stable operation.
While at it, also add voltage constraint overrides for the GPU SRAM
regulator "mt6359_vsram_others" so that we stay in a safe range of
0.75-0.80V.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230301095523.428461-13-angelogioacchino.delregno@collabora.com


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