Don't force RPL MOP configuration in contiki-default-conf.h
Don't force RPL MOP configuration in contiki-default-conf.h

rpl-private.h handles the default MOP correctly, whereas the block in `contiki-default-conf.h` is not only redundant but also fails to handle situations where RPL multicast is required.

arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki