sunxi: add 6.12 as testing kernel
Runtime-tested on:
- Linksprite pcDuino (cortexa8 / sun5i)
- Olimex A20 Micro (cortexa7 / sun7i)
- BananaPi P2 Zero (cortexa7 / sun8i)
- Pine64 SoM (cortexa53 / sun50i)
- Orangepi Zero 2W (cortexa53 / sun50i)
Signed-off-by: Zoltan HERPAI <[email protected]>