perf/arm-cmn: Add debugfs topology info

In general, detailed performance analysis will require knoweldge of the
the SoC beyond the CMN itself - e.g. which actual CPUs/peripherals/etc.
are connected to each node. However for certain development and bringup
tasks it can be useful to have a quick overview of the CMN internal
topology to hand too. Add a debugfs file to map this out.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/159fd4d7e19fb3c8801a8cb64ee73ec50f55903c.1638530442.git.robin.murphy@arm.com


Signed-off-by: Will Deacon <will@kernel.org>