sys/net/nanocoap: fix possible option_count overflow
sys/net/nanocoap: fix possible option_count overflow

RIOT-OS/RIOT,cladmi/RIOT,OlegHahm/RIOT,smlng/RIOT,A-Paul/RIOT,toonst/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,toonst/RIOT,rfuentess/RIOT,authmillenon/RIOT,kaspar030/RIOT,toonst/RIOT,A-Paul/RIOT,ant9000/RIOT,mfrey/RIOT,authmillenon/RIOT,rfuentess/RIOT,authmillenon/RIOT,kYc0o/RIOT,BytesGalore/RIOT,smlng/RIOT,ant9000/RIOT,rfuentess/RIOT,mtausig/RIOT,basilfx/RIOT,x3ro/RIOT,RIOT-OS/RIOT,miri64/RIOT,aeneby/RIOT,miri64/RIOT,BytesGalore/RIOT,lazytech-org/RIOT,x3ro/RIOT,lazytech-org/RIOT,mfrey/RIOT,ant9000/RIOT,rfuentess/RIOT,miri64/RIOT,toonst/RIOT,OlegHahm/RIOT,cladmi/RIOT,x3ro/RIOT,basilfx/RIOT,josephnoir/RIOT,kaspar030/RIOT,OlegHahm/RIOT,BytesGalore/RIOT,kYc0o/RIOT,jasonatran/RIOT,ant9000/RIOT,miri64/RIOT,smlng/RIOT,OTAkeys/RIOT,josephnoir/RIOT,basilfx/RIOT,yogo1212/RIOT,jasonatran/RIOT,josephnoir/RIOT,OlegHahm/RIOT,jasonatran/RIOT,mfrey/RIOT,mtausig/RIOT,josephnoir/RIOT,OTAkeys/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,smlng/RIOT,lazytech-org/RIOT,mtausig/RIOT,cladmi/RIOT,kaspar030/RIOT,kYc0o/RIOT,A-Paul/RIOT,BytesGalore/RIOT,jasonatran/RIOT,aeneby/RIOT,basilfx/RIOT,toonst/RIOT,x3ro/RIOT,kYc0o/RIOT,yogo1212/RIOT,OTAkeys/RIOT,lazytech-org/RIOT,ant9000/RIOT,yogo1212/RIOT,josephnoir/RIOT,mfrey/RIOT,mtausig/RIOT,authmillenon/RIOT,aeneby/RIOT,yogo1212/RIOT,A-Paul/RIOT,smlng/RIOT,cladmi/RIOT,basilfx/RIOT,A-Paul/RIOT,cladmi/RIOT,OTAkeys/RIOT,aeneby/RIOT,BytesGalore/RIOT,kaspar030/RIOT,kaspar030/RIOT,jasonatran/RIOT,authmillenon/RIOT,mtausig/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,aeneby/RIOT,lazytech-org/RIOT,x3ro/RIOT,yogo1212/RIOT,miri64/RIOT,mfrey/RIOT