Make detectBaudrate safe from SYS context, for what it's worth.

Author: dok-net

Diff for: cores/esp8266/HardwareSerial.cpp

@@ -143,7 +143,7 @@ unsigned long HardwareSerial::detectBaudrate(time_t timeoutMillis)
         if ((detectedBaudrate = testBaudrate())) {
           break;
         }
-        delay(100);
+        esp_delay(100);
     }
     return detectedBaudrate;
 }