counters. These counters do not exist on all CPUs, but where they
do exist, can be used for counting events such as dcache misses that
would otherwise be difficult or impossible to instrument by code
inspection or hardware simulation.
pmc(9) is meant to be a general interface. Initially, the Intel XScale
counters are the only ones supported.
Based mostly on NetBSD/prep at this time since the earlier mvme160x
boards are pretty much PReP compliant. Later boards in the range
diverge somewhat from the reference platform, hence the separate port.
Still needs *lots* of bashing into shape, but at this time it will
boot to multi-user over ethernet on an MVME1603-051.
