irqchip/armada-370-xp: Allow allocation of multiple MSIs

Add support for allocating multiple MSIs at the same time, so that the
MSI_FLAG_MULTI_PCI_MSI flag can be added to the msi_domain_info
structure.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1455115621-22846-6-git-send-email-thomas.petazzoni@free-electrons.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>