spapr/xive: remove redundant check in spapr_match_nvt()

spapr/xive: remove redundant check in spapr_match_nvt()

spapr_match_nvt() is a XIVE operation and is used by the machine to
look for a matching target when an event notification is being
delivered. An assert checks that spapr_match_nvt() is called only when
the machine has selected the XIVE interrupt mode but it is redundant
with the XIVE_PRESENTER() dynamic cast.

Apply the cast to spapr->active_intc and remove the assert.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20200106163207.4608-1-clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>