Checking that we're not using the in-kernel XICS is ok with the "xics"
interrupt controller mode, but it is definitely not enough with the
other modes since the guest could be using XIVE.

Ensure XIVE is not in use when emulated XICS RTAS/hypercalls are
called.
Signed-off-by: NGreg Kurz <groug@kaod.org>
Message-Id: <156077253666.424706.6104557911104491047.stgit@bahia.lan>
Reviewed-by: NCédric Le Goater <clg@kaod.org>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>