[examples] Deduplicate RTT examples

Author: salkinium

examples/blue_pill_f103/rtt/main.cpp

@@ -59,6 +59,7 @@ int
 main()
 {
 	Board::initialize();
+	Leds::setOutput();
 
 	MODM_LOG_DEBUG << "Debug" << modm::endl;
 	MODM_LOG_INFO << "Info" << modm::endl;
@@ -83,7 +84,7 @@ main()
 		}
 		if (tmr.execute())
 		{
-			LedNorth::toggle();
+			Leds::toggle();
 
 			MODM_LOG_INFO << "loop: " << counter++ << modm::endl;
 		}

examples/blue_pill_f103/rtt/openocd.cfg

@@ -1,7 +1,12 @@
 <library>
   <extends>modm:disco-f303vc</extends>
+  <!-- <extends>modm:blue-pill-f103</extends> -->
+  <!-- <extends>modm:black-pill-f401</extends> -->
   <options>
+    <option name="modm:platform:rtt:buffer.tx">256</option>
     <option name="modm:platform:rtt:buffer.rx">16</option>
+    <!-- Required for modm:blue-pill-f103, modm:black-pill-f401 -->
+    <!-- <option name="modm:build:openocd.cfg">interface/stlink.cfg</option> -->
   </options>
   <modules>
     <module>modm:platform:rtt</module>