Change in flashrom[master]: dummyflasher.c: Extract params processing into a separate function

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Nico Huber, Edward O'Callaghan, Angel Pons.
Anastasia Klimchuk has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/54748 )

Change subject: dummyflasher.c: Extract params processing into a separate function
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Patch Set 1:

(2 comments)

Patchset:

PS1: 
I noticed something in dummy, not in scope of this patch but maybe for future work, wrote a message below. Thank you!

File dummyflasher.c:

https://review.coreboot.org/c/flashrom/+/54748/comment/f03b8f3b_292cf166 
PS1, Line 26: /* Remove the #define below if you don't want SPI flash chip emulation. */
            : #define EMULATE_SPI_CHIP 1
If this line is removed, dummy does not compile. Because below, if EMULATE_SPI_CHIP is not defined , EMULATE_CHIP won't be defined either - which means emu_data is not defined, so dummy does not compile.

Another thing, if only EMULATE_CHIP is defined (and EMULATE_SPI_CHIP undefined) then dummy does not link, linking fails with an error "undefined reference to `probe_variable_size'".

I wanted to fix that, but I don't know what is expected behaviour behind EMULATE_SPI_CHIP and EMULATE_CHIP, and which combinations of these two flags are valid?
And maybe, we can split into two dummies, dummy_spi and dummy_par, if they are very different?

(I am not changing any behaviour in this patch, but eventually I want to understand what is the correct one).