driver/perf: Remove ARM_SMMU_V3_PMU dependency on ARM_SMMU_V3

The ARM_SMMU_V3_PMU dependency on ARM_SMMU_V3_PMU was added with the idea
that a SMMUv3 PMCG would only exist on a system with an associated SMMUv3.

However it is not the job of Kconfig to make these sorts of decisions (even
if it were true), so remove the dependency.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/1612175042-56866-1-git-send-email-john.garry@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>