ITS specific mappings for SMMUv3/PMCG components can be retrieved
through special index mapping entries introduced in IORT revision C.

Introduce a new API iort_set_device_domain() to set the MSI domain for
SMMUv3/PMCG nodes (extendable to any future IORT node requiring special
index ITS mapping entries) that represent MSI through special index
mappings in order to enable MSI support for the devices their nodes
represent.
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>