This works only temporarily. And the BPI-R2 gets also no IP address. I found an issue, that the service of wpa_supplicant does not automagically start. But I fixed it with:
systemctl enable wpa_supplicant.service
# interfaces(5) file used by ifup(8) and ifdown(8)
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
# The loopback network interface
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto eth1
iface eth1 inet dhcp
auto wlan0
iface wlan0 inet dhcp
wpa-ssid SSID
wpa-psk PSK
But the system start takes about 5 minutes and I have an interface called eth1:avahi