ioapic: kvm: Skip route updates for masked pins

ioapic: kvm: Skip route updates for masked pins

Masked entries will not generate interrupt messages, thus do no need to
be routed by KVM. This is a cosmetic cleanup, just avoiding warnings of
the kind

qemu-system-x86_64: vtd_irte_get: detected non-present IRTE (index=0, high=0xff00, low=0x100)

if the masked entry happens to reference a non-present IRTE.

Cc: qemu-stable@nongnu.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Message-Id: <a84b7e03-f9a8-b577-be27-4d93d1caa1c9@siemens.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>