sunxi: fix missing dt overlays

[EvilOlaf]

Description

overlay subdir was missing vom Makefile, so the overlay creation was skipped.
Has been reported here: https://forum.armbian.com/topic/56756-no-overlays-when-kernel-6181-edge-sunxi-compile/

How Has This Been Tested?

• build https://paste.armbian.de/inebuseleb

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

Summary by CodeRabbit

• New Features
  • Device tree overlay support is now built into Armbian, providing enhanced hardware configuration capabilities and greater customization options for Armbian devices on Allwinner platforms.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

A single line is added to arch/arm/boot/dts/allwinner/Makefile to include the overlay subdirectory in the kernel device-tree build traversal, enabling overlay artifacts to be built alongside existing device-tree sources.

Changes

Cohort / File(s)	Summary
Device-tree overlay build configuration arch/arm/boot/dts/allwinner/Makefile	Added subdir-y := $(dts-dirs) overlay to include overlay subdirectory in the build traversal

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related issues

• Split cb1-overlay.patch into separate patches for overlays and Makefile changes #9088: This PR adds overlay build support to the Makefile, directly enabling device-tree overlay compilation for Allwinner architectures as part of the broader overlay infrastructure improvements.

Suggested reviewers

• igorpecovnik
• leggewie

Poem

🐰 A little line, so small and sweet,
Makes overlay builds complete!
The subdir-y now points the way,
To build more overlays every day! 🌳

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding a missing overlay subdirectory entry to the Makefile to enable device-tree overlay creation for sunxi.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[github-actions]

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