[RFC][OTP] spi: add functions for OTP regions

These are functions for entering/leaving OTP mode and
reading/writing/erasing secure registers.

Also introduces part of the structure that describes OTP, because new
code uses it.

========================================================================

This and other patches marked [OTP] resurrect the work of Hatim
Kanchwala aimed at adding OTP support to flashrom:

    https://blogs.coreboot.org/blog/author/hatim/

This chain of patches is based on my WP tests patches (starts at
CB:59071), which in turn depend on the set of patches that introduce
write-protect support (start at CB:58474).

Due to WP patches not being included in the chain, there are minor
modifications here caused by rebasing.  This will go away once those
changes land on master.

========================================================================

Change-Id: Ic33e2c1de8b0ca02df9118218a663ce63826f339
Signed-off-by: Hatim Kanchwala <hatim at hatimak.me>
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
---
M chipdrivers.h
M flash.h
A otp.h
M spi.h
M spi25.c
5 files changed, 168 insertions(+), 0 deletions(-)