spapr: Disallow unsupported kernel-irqchip settings

spapr: Disallow unsupported kernel-irqchip settings

Split mode doesn't make sense on pseries, neither with XICS nor XIVE. But
passing kernel-irqchip=split silently behaves like kernel-irqchip=on.
Other architectures that support kernel-irqchip do terminate QEMU when
split mode is requested but not available though. Do the same with pseries
for consistency.

Similarly, passing kernel-irqchip=on,accel=tcg starts the machine with the
emulated interrupt controller, ie, behaves like kernel-irqchip=off. However,
when passing  kernel-irqchip=on,accel=kvm, if we can't initialize the KVM
XICS for some reason, ie, xics_kvm_init() fails, then QEMU is terminated.
This is inconsistent. Terminate QEMU all the same when requesting the
in-kernel interrupt controller without KVM.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <154964986747.291716.2679312373018476920.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>