Near-mainline kernel is feature-complete since quite some time, so lets
use that as a default also to simplify boot process, since downstream kernel
depends on various blobs loaded into memory by the bootloader.
Get rid of quirks required in boot process for mainline kernels
also by using a near-mainline u-boot.
Prepare for handling rev b devices.
Keep Downstream kernel to be able to optimize/compare EPD operation
Support the downstream kernel and a close-to-mainline fork. Waveform
data for the eInk display and the Wi-Fi driver are not included yet.
Everything else should work.
