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

arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi

@@ -447,6 +447,13 @@ &mt6359_vrf12_ldo_reg {
 	regulator-always-on;
 };
 
+&mt6359_vsram_others_ldo_reg {
+	regulator-min-microvolt = <750000>;
+	regulator-max-microvolt = <800000>;
+	regulator-coupled-with = <&mt6315_7_vbuck1>;
+	regulator-coupled-max-spread = <10000>;
+};
+
 &mt6359_vufs_ldo_reg {
 	regulator-always-on;
 };
@@ -1411,6 +1418,8 @@ mt6315_7_vbuck1: vbuck1 {
 				regulator-max-microvolt = <800000>;
 				regulator-enable-ramp-delay = <256>;
 				regulator-allowed-modes = <0 1 2>;
+				regulator-coupled-with = <&mt6359_vsram_others_ldo_reg>;
+				regulator-coupled-max-spread = <10000>;
 			};
 		};
 	};