arm64: dts: mediatek: mt8370: Enable gpu support

Add a new gpu node in mt8370.dtsi to enable support for the
ARM Mali G57 MC2 GPU (Valhall-JM) found on the MT8370 SoC, using the
Panfrost driver.

On a Mediatek Genio 510 EVK board, the panfrost driver probed with the
following message:
```
panfrost 13000000.gpu: clock rate = 390000000
panfrost 13000000.gpu: mali-g57 id 0x9093 major 0x0 minor 0x0 status 0x0
panfrost 13000000.gpu: features: 00000000,000019f7, issues: 00000003,
   80000400
panfrost 13000000.gpu: Features: L2:0x08130206 Shader:0x00000000
   Tiler:0x00000809 Mem:0x1 MMU:0x00002830 AS:0xff JS:0x7
panfrost 13000000.gpu: shader_present=0x5 l2_present=0x1
[drm] Initialized panfrost 1.3.0 for 13000000.gpu on minor 0
```

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>

arch/arm64/boot/dts/mediatek/mt8370.dtsi

@@ -59,6 +59,22 @@ &cpu_little3_cooling_map0 {
 				<&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
 };
 
+/*
+ * Please note that overriding compatibles is a discouraged practice and is a
+ * clear indication of nodes not being, well, compatible!
+ *
+ * This is a special case, where the GPU is the same as MT8188, but with one
+ * of the cores fused out in this lower-binned SoC.
+ */
+&gpu {
+	compatible = "mediatek,mt8370-mali", "arm,mali-valhall-jm";
+
+	power-domains = <&spm MT8188_POWER_DOMAIN_MFG2>,
+			<&spm MT8188_POWER_DOMAIN_MFG3>;
+
+	power-domain-names = "core0", "core1";
+};
+
 &ppi_cluster0 {
 	affinity = <&cpu0 &cpu1 &cpu2 &cpu3>;
 };