qemu: fix default devices on sparc machines

The sparc machines have little in common with sparc64 machines.

No sparc machine type includes a PCI bus, so we should not be adding one
to the XML. This further means that we should not be adding a memory
balloon device, nor USB controller as these are both PCI based.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_domain.c

@@ -3561,6 +3561,10 @@ qemuDomainDefAddDefaultDevices(virDomainDefPtr def,
         break;
 
     case VIR_ARCH_SPARC:
+        addDefaultUSB = false;
+        addDefaultMemballoon = false;
+        break;
+
     case VIR_ARCH_SPARC64:
         addPCIRoot = true;
         break;