arch-handbook/scsi: Preen formatting

Go through and fix the bits that the automatic conversion from docbook
got wrong (and/or were wrong before).
o Use [programlisting] for the xxx_ routine declarations
o Un-nest the level of bullet points: make the outer ones sections

or subsections

o get the proper nesting for bits defined in some flags (they were

in some places at the same level)

o Minor code style preening to make thigns a little closer to style(9)

since the examples used differing style.

o Add subsection marking to a few places that didn't get converted to

bullet points, but should have been.

No actual content changes (yet), apart from the new sections. This
document is somewhat out of date in places and needs to be modernized
around locking, synchronization and a few short-cut APIs that used to
need to be spelled out longhand. All that will be in followup commits.

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