UBUNTU: SAUCE: ACPI: platform-msi: retrieve dev id from IORT

UBUNTU: SAUCE: ACPI: platform-msi: retrieve dev id from IORT

For devices connecting to ITS, it needs dev id to identify itself, and
this dev id is represented in the IORT table in named component node
[1] for platform devices, so in this patch we will scan the IORT to
retrieve device's dev id.

With the preparation of iort_node_map_platform_id(), a new API
iort_pmsi_get_dev_id() is introduced for that purpose, call it in
its_pmsi_prepare() to make retrieving dev id ACPI aware.

[1]: https://static.docs.arm.com/den0049/b/DEN0049B_IO_Remapping_Table.pdf

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Ming Lei <ming.lei@canonical.com>
Tested-by: Wei Xu <xuwei5@hisilicon.com>
Tested-by: Sinan Kaya <okaya@codeaurora.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Tomasz Nowicki <tn@semihalf.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
[v8 submission from:
 https://www.spinics.net/lists/arm-kernel/msg555514.html ]
BugLink: http://bugs.launchpad.net/bugs/1669061
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>