Yes, I was just about to write that this is for both radios.

The reasoning was that, for both radios, we don't set the 64-bit address to the RF's registers unless `LINKADDR_SIZE == 8`. Therefore, if we read it under a different `LINKADDR_SIZE`, we will get the RF register's reset values (0x00).

Also, setting the 64-bit address when LINKADDR_SIZE is not 8 will not cause any change whatsoever in terms of how the radio will behave, hence the same test in `set_object`.

I don't feel very strongly about this. Easy to change if you feel it needs changed.