hw/acpi: Remove superfluous return statement

The "return;" statement at the end of acpi_memory_plug_cb()
does not make much sense, so let's remove it.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

hw/acpi/memory_hotplug.c

@@ -250,7 +250,6 @@ void acpi_memory_plug_cb(ACPIREGS *ar, qemu_irq irq, MemHotplugState *mem_st,
         /* do ACPI magic */
         acpi_send_gpe_event(ar, irq, ACPI_MEMORY_HOTPLUG_STATUS);
     }
-    return;
 }
 
 void acpi_memory_unplug_request_cb(ACPIREGS *ar, qemu_irq irq,