uart: add ledctrl app

uart/util.c

@@ -0,0 +1,11 @@
+#define CYCLES_PER_MS 6666  // ish
+
+/** waits a general amount of time */
+void busy_sleep(int ms) {
+  for (int i = 0; i < ms; ++i) {
+    // wait for 1 ms
+    for (int i = 0; i < CYCLES_PER_MS; ++i) {
+      // nothing
+    }
+  }
+}