ppc/spapr: Allow FWNMI on TCG

ppc/spapr: Allow FWNMI on TCG

There should no longer be a reason to prevent TCG providing FWNMI.
System Reset interrupts are generated to the guest with nmi monitor
command and H_SIGNAL_SYS_RESET. Machine Checks can not be injected
currently, but this could be implemented with the mce monitor cmd
similarly to i386.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20200316142613.121089-6-npiggin@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
[dwg: Re-enable FWNMI in qtests, since that now works]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>