iommu/arm-smmu: Account for PMU interrupts

In preparation for SMMUv2 PMU support, rejig our IRQ setup code to
account for PMU interrupts as additional resources. We can simplify the
whole flow by only storing the context IRQs, since the global IRQs are
devres-managed and we never refer to them beyond the initial request.

CC: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/b2a40caaf1622eb35c555074a0d72f4f0513cff9.1645106346.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>