Change in flashrom[master]: sysfsgpio.c implement spi interface via linux sysfs

[Xiang Wang (Code Review)]

Attention is currently required from: Stefan Reinauer, Angel Pons.
Hello build bot (Jenkins), Stefan Reinauer, Edward O'Callaghan,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/flashrom/+/49254

to look at the new patch set (#6).

Change subject: sysfsgpio.c implement spi interface via linux sysfs
......................................................................

sysfsgpio.c implement spi interface via linux sysfs

Linux can operate gpio through sysfs, this patch implements a bitbang
spi interface through sysfs. Through this patch, some SBC can be used
as flash programmers.

TEST=build and run flashrom with sysfsgpio on raspberrypi to read  W25Q128.V

Change-Id: I1bc47ef8011bba560326b501a80869340bb9f733
Signed-off-by: Xiang Wang 
---
M Makefile
M flashrom.c
M meson.build
M programmer.h
A sysfsgpio.c
5 files changed, 279 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/54/49254/6