perf/arm-cmn: Demarcate CMN-600 specifics

In preparation for supporting newer CMN products, let's introduce a
means to differentiate the features and events which are specific to a
particular IP from those which remain common to the whole family. The
newer designs have also smoothed off some of the rough edges in terms
of discoverability, so separate out the parts of the flow which have
effectively now become CMN-600 quirks.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/9f6368cdca4c821d801138939508a5bba54ccabb.1638530442.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>