Change in flashrom[master]: [RFC] spi_master: Add shutdown function in spi_master struct

[Nico Huber (Code Review)]

Attention is currently required from: Thomas Heijligen, Edward O'Callaghan, Angel Pons, Anastasia Klimchuk.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/55932 )

Change subject: [RFC] spi_master: Add shutdown function in spi_master struct
......................................................................

Patch Set 2:

(1 comment)

Patchset:

PS1:
> thank you, this is actually very useful! (as usual!) […]

The "few" wasn't meant literally :)

About other masters, well, it's not very obvious indeed. As always it's
hard to see/show absence of something. And it turns out that the `internal`
programer might actually be the only case of this:

Let's see what files have a `struct programmer_entry`:

$ git grep -l '^const struct programmer_entry ' *.c

and which call some `register_*master()`:

$ git grep -l '<register_([a-z_]*)master(' *.c

and compare the two:

$ diff -u <(git grep -l '^const struct programmer_entry ' *.c) <(git grep -l '<register_([a-z_]*)master(' *.c)

Some of it is noise (opaque.c, bitbang_spi.c, programmer.c are just
infrastructure). But there are some masters without a programmer entry:

* ichspi.c
* it85spi.c
* it87spi.c
* mcp6x_spi.c
* sb600spi.c
* wbsio_spi.c

All files not touched by commit 4f5169df. And I assume all part of the
`internal` programmer.