cpu/esp32: esp_eth doesn't call memcpy if iol_len is 0
cpu/esp32: esp_eth doesn't call memcpy if iol_len is 0


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