perf/arm-cmn: Permit more exhaustive groups

The group validation logic still somewhat assumes the original CMN-600
case of events counting globally, such that if one tries to group 9
events where the first 8 target a single DTC domain, the 9th will be
rejected because *a* DTC domain is full, even though it might only
target other non-overlapping domains and thus still be schedulable.
Improve matters by only counting the DTCs that the new event actually
needs (as arm_cmn_val_add_event() was already clever enough to do).

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-and-tested-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Link: https://lore.kernel.org/r/bdfd1e58dac449e407c5cacfd6bf8577dc0a5899.1733943898.git.robin.murphy@arm.com


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