memory-device: fix error message when hinted address is too small

The "at" should actually be a "before".
    if (new_addr < address_space_start)
     -> "can't add memory ... before... $address_space_start"

So it looks similar to the other check
    } else if ((new_addr + size) > address_space_end)
     -> "can't add memory ... beyond..."

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20181005092024.14344-3-david@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

hw/mem/memory-device.c

@@ -146,7 +146,8 @@ uint64_t memory_device_get_free_addr(MachineState *ms, const uint64_t *hint,
         new_addr = *hint;
         if (new_addr < address_space_start) {
             error_setg(errp, "can't add memory [0x%" PRIx64 ":0x%" PRIx64
-                       "] at 0x%" PRIx64, new_addr, size, address_space_start);
+                       "] before 0x%" PRIx64, new_addr, size,
+                       address_space_start);
             return 0;
         } else if ((new_addr + size) > address_space_end) {
             error_setg(errp, "can't add memory [0x%" PRIx64 ":0x%" PRIx64