Disable debug options and SMP, and remove support for other platforms.
Unixbench reports a speedup for process creation and syscalls, from
Process Creation 126.0 1043.8 82.8
System Call Overhead 15000.0 235497.3 157.0
to
Process Creation 126.0 1826.7 145.0
System Call Overhead 15000.0 421030.2 280.7
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.