perf/arm-cmn: Remove CMN-600 DTC domain special case

The special case for trying to infer the DTC domain for DTC-adjacent
nodes on CMN-600 is fragile and buggy - currently resulting in subtly
messed up DTC counter allocation - and the theoretical benefit it
offers to a tiny minority of use-cases arguably doesn't outweigh the
inconsistency it offers to others anyway. Just get rid of it.

Fixes: ab33c66f ("perf/arm-cmn: Enable per-DTC counter allocation")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/67985e39f53b56385d79a4f1264cf7f9cacedb58.1742308248.git.robin.murphy@arm.com


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