cpu/esp: simplified esp_now_netdev::_recv function
cpu/esp: simplified esp_now_netdev::_recv function

Simplifies the _recv receive function structure of esp_now_netdev according to the possible parameter values.
ant9000/RIOT,aeneby/RIOT,rfuentess/RIOT,aeneby/RIOT,mtausig/RIOT,OTAkeys/RIOT,authmillenon/RIOT,lazytech-org/RIOT,kYc0o/RIOT,basilfx/RIOT,x3ro/RIOT,lazytech-org/RIOT,BytesGalore/RIOT,authmillenon/RIOT,rfuentess/RIOT,josephnoir/RIOT,kaspar030/RIOT,kYc0o/RIOT,miri64/RIOT,josephnoir/RIOT,yogo1212/RIOT,kaspar030/RIOT,mtausig/RIOT,yogo1212/RIOT,josephnoir/RIOT,josephnoir/RIOT,A-Paul/RIOT,x3ro/RIOT,toonst/RIOT,jasonatran/RIOT,yogo1212/RIOT,kYc0o/RIOT,smlng/RIOT,ant9000/RIOT,smlng/RIOT,lazytech-org/RIOT,yogo1212/RIOT,miri64/RIOT,smlng/RIOT,toonst/RIOT,cladmi/RIOT,miri64/RIOT,mfrey/RIOT,BytesGalore/RIOT,yogo1212/RIOT,basilfx/RIOT,jasonatran/RIOT,BytesGalore/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,kYc0o/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,miri64/RIOT,toonst/RIOT,A-Paul/RIOT,authmillenon/RIOT,OlegHahm/RIOT,mtausig/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,ant9000/RIOT,lazytech-org/RIOT,jasonatran/RIOT,miri64/RIOT,aeneby/RIOT,smlng/RIOT,lazytech-org/RIOT,mtausig/RIOT,basilfx/RIOT,BytesGalore/RIOT,mfrey/RIOT,OTAkeys/RIOT,x3ro/RIOT,OTAkeys/RIOT,ant9000/RIOT,ant9000/RIOT,kaspar030/RIOT,mfrey/RIOT,toonst/RIOT,authmillenon/RIOT,rfuentess/RIOT,OlegHahm/RIOT,x3ro/RIOT,yogo1212/RIOT,aeneby/RIOT,OlegHahm/RIOT,mtausig/RIOT,toonst/RIOT,basilfx/RIOT,OlegHahm/RIOT,x3ro/RIOT,mfrey/RIOT,cladmi/RIOT,rfuentess/RIOT,mfrey/RIOT,rfuentess/RIOT,cladmi/RIOT,josephnoir/RIOT,cladmi/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,authmillenon/RIOT,authmillenon/RIOT,A-Paul/RIOT,A-Paul/RIOT,jasonatran/RIOT,smlng/RIOT,kYc0o/RIOT,kaspar030/RIOT,aeneby/RIOT,RIOT-OS/RIOT,basilfx/RIOT,RIOT-OS/RIOT,BytesGalore/RIOT,cladmi/RIOT