UBUNTU: SAUCE: irqchip: gicv3-its: platform-msi: refactor its_pmsi_init() to prepare...

UBUNTU: SAUCE: irqchip: gicv3-its: platform-msi: refactor its_pmsi_init() to prepare for ACPI

Introduce its_pmsi_init_one() to refactor the code to isolate
ACPI&DT common code to prepare for ACPI later.

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Reviewed-by: Matthias Brugger <mbrugger@suse.com>
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: Tomasz Nowicki <tn@semihalf.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
[v8 submission from:
 https://www.spinics.net/lists/arm-kernel/msg555502.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>