Change in flashrom[master]: raiden_debug_spi: Link spi_master struct to spi data

[Nico Huber (Code Review)]

Attention is currently required from: Edward O'Callaghan, Angel Pons, Anastasia Klimchuk, Nikolai Artemiev.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/57972 )

Change subject: raiden_debug_spi: Link spi_master struct to spi data
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Patch Set 1: Code-Review+2

(1 comment)

File raiden_debug_spi.c:

https://review.coreboot.org/c/flashrom/+/57972/comment/5d299c7a_f6b25a52 
PS1, Line 444: spi_config
Could we just call the field `spi_master` too? I think that would make
things more clear to the reader of code that accesses it.

After reading the rest of the patch: It seems consistent that way and
if we want to change it, we could change all `spi_config` occurences
later.