[flashrom] Add support for EN29LV800(A/B/C) (was: Confirm EN29LV800 bus, timing, and page size)

[Stefan Tauner]

This is based on TJ's patches from 2010, see
http://patchwork.coreboot.org/patch/883/
http://patchwork.coreboot.org/patch/884/

I have rebased and combined them, added voltages, corrected the names
and verified the erase block layouts. Someone else needs to
review/change the parallel-specific parts, because i have no idea about
all those jedec vs. 3-byte vs. shifted problems (and i actually do not
want to know :P).