hw: acpi: Fix memory hotplug AML generation error

When using the generated memory hotplug AML, the iasl
compiler would give the following error:

dsdt.dsl 266: Return (MOST (_UID, Arg0, Arg1, Arg2))
Error 6080 - Called method returns no value ^

Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/memory_hotplug.c

@@ -686,15 +686,15 @@ void build_memory_hotplug_aml(Aml *table, uint32_t nr_mem,
 
             method = aml_method("_OST", 3, AML_NOTSERIALIZED);
             s = MEMORY_SLOT_OST_METHOD;
-            aml_append(method, aml_return(aml_call4(
-                s, aml_name("_UID"), aml_arg(0), aml_arg(1), aml_arg(2)
-            )));
+            aml_append(method,
+                       aml_call4(s, aml_name("_UID"), aml_arg(0),
+                                 aml_arg(1), aml_arg(2)));
             aml_append(dev, method);
 
             method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
             s = MEMORY_SLOT_EJECT_METHOD;
-            aml_append(method, aml_return(aml_call2(
-                       s, aml_name("_UID"), aml_arg(0))));
+            aml_append(method,
+                       aml_call2(s, aml_name("_UID"), aml_arg(0)));
             aml_append(dev, method);
 
             aml_append(dev_container, dev);