openpic: make register names correspond better with hw docs

openpic: make register names correspond better with hw docs

The base openpic specification doesn't provide abbreviated register
names, so it's somewhat understandable that the QEMU code made up
its own, except that most of the names that QEMU used didn't correspond
to the terminology used by any implementation I could find.

In some cases, like PCTP, the phrase "processor current task priority"
could be found in the openpic spec when describing the concept, but
the register itself was labelled "current task priority register"
and every implementation seems to use either CTPR or the full phrase.

In other cases, individual implementations disagree on what to call
the register.  The implementations I have documentation for are
Freescale, Raven (MCP750), and IBM.  The Raven docs tend to not use
abbreviations at all.  The IBM MPIC isn't implemented in QEMU.  Thus,
where there's disagreement I chose to use the Freescale abbreviations.

Signed-off-by: Scott Wood <scottwood@freescale.com>
[agraf: rebase on current state of the code]
Signed-off-by: Alexander Graf <agraf@suse.de>