iommu/amd: Remove useless irq affinity notifier

iommu->intcapxt_notify field is no longer used
after a switch to a separate domain was done

Fixes: d1adcfbb

 ("iommu/amd: Fix IOMMU interrupt generation in X2APIC mode")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20211123161038.48009-6-mlevitsk@redhat.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>