MAC address settings set by RCX_SET_MAC_ADDR_REQ not applied to low level

Since the packet RCX_SET_MAC_ADDR_REQ is handled directly by the rcX Middleware task, a new MAC address set by the user application is only stored in this level. The stack actually checks the data provider settings from rcX once in the startup and never changes the MAC address again.

In case of devices without SecMem or FDL, the stack is confgured with the invalid MAC address 00:00:00:00:00:00