Change in flashrom[master]: Add unit test to run init/shutdown for enabled drivers

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Anastasia Klimchuk.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/51487 )

Change subject: Add unit test to run init/shutdown for enabled drivers
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Patch Set 1:

(1 comment)

File mec1308.c:

https://review.coreboot.org/c/flashrom/+/51487/comment/8440124f_ff22057f 
PS1, Line 115: #endif /* UNIT_TEST_ENV */
> I was thinking about separate compilation units for a while, how exactly to do this. […]

I guess we could have something like a `hwaccess_unittest.h`, yes. It could be
hooked up via `-include` and `#define __HW_ACCESS_H__`. This way the original
`hwaccess.h` would be bypassed.

It could provide a single definition for the used macros, e.g.

#define OUTB(v, p) test_outb(v, p)
    #define INB(p) test_inb(p)

etc.

However, the original `hwaccess.h` provides more than the I/O macros. Maybe
we should split that out?

There are probably many ways to solve the per-driver mocking issue. Two ideas
from the top of my head:

1. Build multiple test binaries, each with its own versions of test_outb() etc.

2. Provide some abstraction via function pointers. e.g. a struct per test with

struct test_io {
            void (*outb)(unsigned char value, unsigned short port);
            unsigned char (*inb)(unsigned short port);
            /* etc. */
    }
    extern const struct test_io *test_io;

And then before each test, set

test_io = test_io_mec1308;

The test_*() functions would then simply call the respective function in
`test_io`, e.g.:

void test_outb(unsigned char value, unsigned short port)
    {
            test_io->outb(value, port);
    }