iommu/arm-smmu-v3: Parse PASID devicetree property of platform devices

For platform devices that support SubstreamID (SSID), firmware provides
the number of supported SSID bits. Restrict it to what the SMMU supports
and cache it into master->ssid_bits, which will also be used for PCI
PASID.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>