arm64: perf/kvm: Use a common PMU cycle counter define

The PMUv3 and KVM code each have a define for the PMU cycle counter
index. Move KVM's define to a shared location and use it for PMUv3
driver.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20240731-arm-pmu-3-9-icntr-v3-5-280a8d7ff465@kernel.org


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