Fix for aes_encrypt() conflict with built-in function on ESP8266 and ESP32

[lyusupov]

This issue is a 'comeback' from year 2016. It was fixed in LMIC but still remains in BASICMAC. Details are:

• https://github.com/matthijskooijman/arduino-lmic/issues/24/ and
• https://github.com/matthijskooijman/arduino-lmic/commit/e9ae35136beae545fded5831ae98a962e00f2e12#diff-16b9479e2c4b7ec030c4233f27bf6344

[matthijskooijman]

Thanks for your pull request and the detailed links :-) I've manually merged your commit into master, so I'm closing this one.