Allwinner DT changes for 5.2
This PR is pretty significant, but it been mostly about:
- Fixing the DTC warnings in most of our DT. We're now down to 2
warnings, from several thousands.
- Fixing a good number of minor issues, typos, and so on thanks to the DT
validation tools
- Describe the MBUS controller and the special DMA RAM mapping on the A13
- Add support for the LRADC on the A83t
- Add support for the I2C bus used for the PMIC on the A33
- Start using the DT annotation /omit-if-no-ref/ on our pinctrl nodes