arm64: dts: enable Panthor GPU node on reComputer RK3588

[weicheng04]

What

Switch the reComputer RK3588 DevKit GPU device tree configuration from the vendor Mali kbase node to the Panthor DRM node.

This PR changes:

• &gpu
  • set status = "disabled"
• &gpu_panthor
  • reuse the existing GPU supplies
  • set status = "okay"

Why

reComputer RK3588 DevKit uses Mali-G610, which is a Valhall CSF GPU. The RK3588 device tree already has two GPU descriptions for the same hardware address:

• gpu@fb000000 for the vendor Mali kbase driver
• gpu-panthor@fb000000 for the upstream Panthor DRM driver

Only one of these nodes can own the GPU. To use the Panthor/Mesa graphics stack, the vendor Mali node must be disabled and the Panthor node must be enabled.

This is part of the fix for the RK3588 4K DP/HDMI hotplug issue. Testing showed the kernel display pipeline can modeset 4K correctly, but the closed Mali userspace GBM path fails framebuffer creation during
Xorg hotplug with drmModeAddFB2 returning -ENOENT.

Switching to Panthor + Mesa avoids the closed Mali GBM path while keeping GPU acceleration.

Related Armbian PR

This DTS change should be used together with the Armbian build change that enables the Panthor/Mesa userspace stack for reComputer RK3588 DevKit:

armbian-build: fix/rk3588-panthor-display-hotplug

That Armbian change:

- enables CONFIG_DRM_PANTHOR
- disables the vendor Mali kbase configs
- skips closed Mali userspace packages
- installs Mesa 25 from bookworm-backports
- installs the Mali CSF firmware

Without this DTS change, the kernel config/userspace change alone is not enough because the board still exposes the GPU through the vendor Mali node.

## Tested

Tested on reComputer RK3588 DevKit with a Bookworm GNOME desktop image using the paired Armbian Panthor/Mesa stack.

Verified:

- Panthor binds to fb000000.gpu-panthor
- CSF firmware loads successfully
- OpenGL renderer reports Mali-G610 (Panfrost)
- DP 4K60 hotplug works
- HDMI 4K60 hotplug works
- GPU acceleration is available