Allwinner DT changes for 4.8, take 2
Another set of changes for the 4.8 merge window, among which:
- Reworking of the DT for the tablets based on Allwinner reference design
and q8 designs to avoid duplication as much as possible
- Renaming a DT merged in the first PR for consistency
- Enable a few devices on some boards
- New boards: Polaroid MID2407PXE03, inet86dz