shell/sc_gnrc_netif: use fmt_is_number()
shell/sc_gnrc_netif: use fmt_is_number()

smlng/RIOT,x3ro/RIOT,mtausig/RIOT,kYc0o/RIOT,josephnoir/RIOT,kYc0o/RIOT,authmillenon/RIOT,basilfx/RIOT,mtausig/RIOT,smlng/RIOT,yogo1212/RIOT,toonst/RIOT,OTAkeys/RIOT,yogo1212/RIOT,miri64/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,jasonatran/RIOT,toonst/RIOT,authmillenon/RIOT,josephnoir/RIOT,josephnoir/RIOT,aeneby/RIOT,kaspar030/RIOT,ant9000/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,authmillenon/RIOT,yogo1212/RIOT,jasonatran/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,basilfx/RIOT,miri64/RIOT,x3ro/RIOT,authmillenon/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,mtausig/RIOT,miri64/RIOT,OlegHahm/RIOT,basilfx/RIOT,x3ro/RIOT,miri64/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,mtausig/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,aeneby/RIOT,toonst/RIOT,jasonatran/RIOT,kaspar030/RIOT,ant9000/RIOT,authmillenon/RIOT,jasonatran/RIOT,kaspar030/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,smlng/RIOT,OlegHahm/RIOT,miri64/RIOT,ant9000/RIOT,ant9000/RIOT,aeneby/RIOT,mtausig/RIOT,authmillenon/RIOT,kYc0o/RIOT,aeneby/RIOT,yogo1212/RIOT,aeneby/RIOT,jasonatran/RIOT,toonst/RIOT,smlng/RIOT,OTAkeys/RIOT,smlng/RIOT,kaspar030/RIOT,basilfx/RIOT,basilfx/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,ant9000/RIOT,x3ro/RIOT,toonst/RIOT,x3ro/RIOT