Add support for Recore

[eliasbakken]

Description

This PR adds support for Recore A5, A6, and A7 hardware. Recore is a 3D printer control board based on Allwinner A64.
Since the board uses the AR100 for real time stepping, the SCP is disabled and instead a version of Klipper is loaded instead.

How Has This Been Tested?

The patches have been tested by building the current and legacy kernels with the minimal images.

• Minimal image with current kernel
• Minimal image with legacy kernel

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
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[igorpecovnik]

Add recently added variable BOARD_MAINTAINER="eliasbakken" to board config, the rest looks OK.

[eliasbakken]

I did not see any references to BOARD_MAINTAINER anywhere in the code, but I've added it now.

[igorpecovnik]

Thanks.

I did not see any references

It was merged today.