arm64: PCI/MSI: Use asm-generic/msi.h

In order to support CONFIG_GENERIC_MSI_IRQ_DOMAIN, we need to
define msi_alloc_info_t. As the generic version exposed in
asm-generic/msi.h is perfectly convenient, import this file
as asm/msi.h.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1416839720-18400-2-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>