intel-iommu: correct the value used for error_setg_errno()

intel-iommu: correct the value used for error_setg_errno()

error_setg_errno() expects a normal errno value, not a negated
one, so we should use ENOTSUP instead of -ENOSUP.

Fixes: Coverity CID 1487174
Fixes: ("intel_iommu: support snoop control")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220401022824.9337-1-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>