On ESP8266, setSS() does not work when using GPIO16 as CS pin

[rayshobby]

On ESP8266, this works for all other GPIO pins except when GPIO 16 is used as CS:

Ethernet/src/utility/w5100.h

Line 415 in 75a3c37

GPOC = ss_pin_mask;

Reference ESP8266's digitalWrite function:
https://github.com/esp8266/Arduino/blob/master/cores/esp8266/core_esp8266_wiring_digital.cpp#L84