iommu/amd: Add IOAPIC remapping routines

Add the routine to setup interrupt remapping for ioapic
interrupts. Also add a routine to change the affinity of an
irq and to free an irq allocation for interrupt remapping.
The last two functions will also be used for MSI interrupts.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>