Add community support for Rock5B+

[HeyMeco]

Description

After adding the device tree to armbian/rockchip-linux and it being tested on real HW to confirm functionality this is the last step to add Rock5B+ to the build system.
I'm considering maintaining this board in the future but for now this is a community addition

How Has This Been Tested?

• Build the image successfully locally
• Ran the image on real HW (see the link above to armbian/rockchip-linux)

Checklist:

Please delete options that are not relevant.

• 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