arm64: dts: mt8183-pumpkin: Couple VGPU and VSRAM_GPU regulators

Add coupling for these regulators, as they have a strict voltage output
relation to satisfy in order to ensure GPU stable operation.
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/20230301095523.428461-5-angelogioacchino.delregno@collabora.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8183-pumpkin.dts

@@ -71,7 +71,6 @@ &auxadc {
 
 &gpu {
 	mali-supply = <&mt6358_vgpu_reg>;
-	sram-supply = <&mt6358_vsram_gpu_reg>;
 };
 
 &i2c0 {
@@ -176,6 +175,16 @@ &mmc1 {
 	non-removable;
 };
 
+&mt6358_vgpu_reg {
+	regulator-coupled-with = <&mt6358_vsram_gpu_reg>;
+	regulator-coupled-max-spread = <100000>;
+};
+
+&mt6358_vsram_gpu_reg {
+	regulator-coupled-with = <&mt6358_vgpu_reg>;
+	regulator-coupled-max-spread = <100000>;
+};
+
 &pio {
 	i2c_pins_0: i2c0 {
 		pins_i2c{