perf/smmuv3: Add devicetree support

Add device-tree support to the SMMUv3 PMCG driver.

Signed-off-by: Jay Chen <jkchen@linux.alibaba.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20211117144844.241072-3-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>