kvm: Activate in-kernel irqchip support

Make the basic in-kernel irqchip support selectable via
-machine ...,kernel_irqchip=on. Leave it off by default until it can
fully replace user space models.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

qemu-config.c

@@ -531,6 +531,10 @@ static QemuOptsList qemu_machine_opts = {
             .name = "accel",
             .type = QEMU_OPT_STRING,
             .help = "accelerator list",
+        }, {
+            .name = "kernel_irqchip",
+            .type = QEMU_OPT_BOOL,
+            .help = "use KVM in-kernel irqchip",
         },
         { /* End of list */ }
     },