[coreboot] Kconfig: Move `CBFS_SIZE` out of main section

[Peter Stuge]

Julius Werner wrote:
> > I'd also like the interface to be friendlier. What granularity is
> > actually supported for the option? I doubt that it's single bytes?
> >
> > Maybe make it decimal kb? The default value depends on ROM_SIZE, right?
> 
> I would very much prefer it to stay byte sized. This makes the
> Makefiles that use it easier to write

It's trivial to add another variable between the user interface and
Makefile rules to turn the friendly value into what's convenient for
the code.


> and avoids confusion compared to the byte sized CONFIG_ROM_SIZE.

The big difference is that users never see the actual ROM_SIZE value.

They see a friendly list of common flash chip sizes, with the default
being what ships with the particular board.


> The actually supported granularity is anything that CBFS/cbfstool
> supports as an image size, which I think is in theory arbitrary down
> to individual bytes.

What are the common CBFS_SIZE values?


//Peter