flashrom: import chip restore handler from cros flashrom

Allows drivers to register a callback function that gets
called to reset the chip state once programming has finished.

This is used by the s25f driver added in a subsequent patch,
which changes chips with a hybrid (non-uniformly sized) sector
layout to a uniform layout, and registers a restore function
to change the chip back to the hybrid layout at exit.

BUG=b:153800073
BRANCH=none
TEST=builds

Change-Id: I2a522dc1fd3952793fbcad70afc6dd43850fbbc5
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
---
M flash.h
M flashrom.c
2 files changed, 41 insertions(+), 0 deletions(-)