Adding support for the Speedport W504V

This 8/64 device is supported by OpenWRT. But as it requires opening the case
to access the UART for flashing, it is not eligible to be added to the mainline gluon.

targets/lantiq-xway

@@ -12,6 +12,11 @@ device('avm-fritz-box-7312', 'avm_fritz7312', {
 	factory = false,
 })
 
+device('speedport-w504v', 'arcadyan_arv8539pw22', {
+	factory = false,
+	broken = true, -- barely tested, cannot be flashed without opening the case
+})
+
 device('netgear-dgn3500b', 'netgear_dgn3500b', {
 	factory_ext = '.img',
 })