Many changes make proto boards very hard to work with since
proto boards were using A stepping processors. Everyone has
moved on. Therefore, drop non-proto support.
BUG=chrome-os-partner:56791
Change-Id: I2985e3965b1b69445e22506bd664b4cbca13c8ab
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16377
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: build bot (Jenkins)