WPS causes wdt reset

Tracking the WPS issue:
ref: https://github.com/espressif/ESP8266_NONOS_SDK/issues/130
cause: PR[#4622](https://github.com/esp8266/Arduino/pull/4622#issuecomment-392303906)
discussion: [bearssl#2](https://github.com/earlephilhower/bearssl-esp8266/issues/2)
fix: #4889