Do not call yield() from timedRead() or timedPeek() when _timeout is set to 0. (#6242)

Author: mhightower83

Diff for: cores/esp8266/Stream.cpp

@@ -33,6 +33,8 @@ int Stream::timedRead() {
         c = read();
         if(c >= 0)
             return c;
+        if(_timeout == 0)
+            return -1;
         yield();
     } while(millis() - _startMillis < _timeout);
     return -1;     // -1 indicates timeout
@@ -46,6 +48,8 @@ int Stream::timedPeek() {
         c = peek();
         if(c >= 0)
             return c;
+        if(_timeout == 0)
+            return -1;
         yield();
     } while(millis() - _startMillis < _timeout);
     return -1;     // -1 indicates timeout
@@ -254,4 +258,3 @@ String Stream::readStringUntil(char terminator) {
     }
     return ret;
 }
-