WIP: arm64: Add GPU nodes for MT8192

The MediaTek MT8192 includes a Mali-G57 GPU supported in Panfrost. Add
the GPU node to the device tree to enable 3D acceleration.

WIP because this device tree is wrong (missing clocks).
Needs clk_ignore_unused to work.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>