On pocketbook, update modes are not as clear cut due to overall
chipset and kernel version mess. Inkview solves this by always
using the slowest (and safe) GC16 waveform. We now do that too
by default.
Slow updates suck though, so there's now a menu entry to configure
it for speed (with mild artifacts at best, kernel panic at worst).
This is a generic interface (any eink Screen can announce support).
The driver may interpret the slow/fast range however they want.
