nicira: nx_output_reg can infer nbits
nicira: nx_output_reg can infer nbits

Other code could already do this.  Now this can too.

MurphyMc/pox,noxrepo/pox,MurphyMc/pox,pthien92/sdn,noxrepo/pox,pthien92/sdn,pthien92/sdn,noxrepo/pox,MurphyMc/pox,noxrepo/pox,pthien92/sdn,MurphyMc/pox,MurphyMc/pox,pthien92/sdn