kvm: Decouple 'MSI routing via irqfds' from 'kernel irqchip'

Decouple another x86-specific assumption about what irqchips imply.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 8c28fca..7a874ea 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -2048,7 +2048,9 @@
         no_hpet = 1;
     }
     /* We know at this point that we're using the in-kernel
-     * irqchip, so we can use irqfds.
+     * irqchip, so we can use irqfds, and on x86 we know
+     * we can use msi via irqfd.
      */
     kvm_irqfds_allowed = true;
+    kvm_msi_via_irqfd_allowed = true;
 }