AMD IOMMU: only translate remapped IO-APIC RTEs

AMD IOMMU: only translate remapped IO-APIC RTEs

1aeb1156fa ("x86 don't change affinity with interrupt unmasked")
introducing RTE reads prior to the respective interrupt having got
enabled for the first time uncovered a bug in 2ca9fbd739 ("AMD IOMMU:
allocate IRTE entries instead of using a static mapping"): We obviously
shouldn't be translating RTEs for which remapping didn't get set up
yet.

Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>