The "arm,armv8-pmuv3" compatible is intended only for s/w models. Primarily,
it doesn't provide any detail on uarch specific events.
There's still remaining cases for CPUs without any corresponding PMU
definition and for big.LITTLE systems which only have a single PMU node
(there should be one per core type).
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>