Change in flashrom[master]: programmer: Smoothen register_par_master API

[Edward O'Callaghan (Code Review)]

Attention is currently required from: Nico Huber, Angel Pons, Anastasia Klimchuk.
Edward O'Callaghan has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/54169 )

Change subject: programmer: Smoothen register_par_master API
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Patch Set 3:

(1 comment)

File programmer.c:

https://review.coreboot.org/c/flashrom/+/54169/comment/5a142db1_6258313b 
PS3, Line 100: if (data)
> While this is consistent with the other patches already merged so maybe worth doing as a cleanup pat […]

Just to clarify some ambiguity in my writing here. The manual cases of `data` getting set in the drivers, which this branch is effectively working around, just be collapsed instead of the intermediate workaround here.