rockchip: RK3506: Increase DMA coherent pool

[vidplace7]

Description

Increases DMA coherent_pool from 4M to 8M on RK3506.

Fixes issues with ethernet / USB / SPI init on RK3506 boards.

How Has This Been Tested?

• ebyte-ecb41-pge tested change in /boot/armbianEnv.txt -- ethernet works and USB inits (both broken before)
• luckfox-lyra-plus tested change in /boot/armbianEnv.txt -- fixes enabling SPI when Ethernet is in use (currently broken)

Checklist:

• I have performed a self-review of my own code

Summary by CodeRabbit

• Chores
  • Updated memory pool allocation configuration in boot environment settings.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 411dd61e-0673-48c5-82a9-838a5bc38e99

📥 Commits

Reviewing files that changed from the base of the PR and between 28862c7 and a036c69.

📒 Files selected for processing (1)

• config/bootenv/rk3506.txt

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📝 Walkthrough

Walkthrough

The coherent pool size configuration for the RK3506 boot environment was increased from 4M to 8M. This single configuration parameter adjustment affects memory allocation settings for the bootloader.

Changes

Cohort / File(s)	Summary
Boot Configuration config/bootenv/rk3506.txt	Increased coherent_pool parameter from 4M to 8M in kernel boot arguments.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐰 A pool of bytes, now double in size,
From four to eight—a modest surprise!
The RK3506 breathes deeper today,
More memory dancing in a coherent way.
✨ Hop forward, dear config!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately summarizes the main change: increasing the DMA coherent pool size for RK3506, which directly corresponds to the modification in config/bootenv/rk3506.txt.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

✅ This PR has been reviewed and approved — all set for merge!