arm64: dts: mediatek: mt8370: Enable gpu support

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>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250509-mt8370-enable-gpu-v6-5-2833888cb1d3@collabora.com