[coreboot-gerrit] Change in coreboot[master]: Drop explicit NULL initializations from `device_operations`

[Nico Huber (Code Review)]

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/40126 )

Change subject: Drop explicit NULL initializations from `device_operations`
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Patch Set 6:
> What was the DEVICE_NOOP introduced for then?

Looking at the patches that introduced and used it, there
was a lack of communication I guess. At first it was used
to replace individual no-op functions, but later also to
replace NULL pointers. The latter often makes no sense.

Why have no-op function pointers? `.read_resources` and
`.set_resources` are considered mandatory with exceptions
in cases somebody reasoned about it (usually nobody did
because the code was just copy-pasted). That's when one
should use DEVICE_NOOP.

We always check for NULL pointers in the operations, so
using NULL (or ommitting) everything else seems fine.