Fix ADB missing keystrokes problem Thanks, blargg! #14

- Add delay between scans to prevent overlaod of ADB keyboard controllers
- <http://geekhack.org/index.php?topic=14290.msg1068919#msg1068919>

protocol/adb.c

@@ -83,6 +83,12 @@ bool adb_host_psw(void)
 }
 #endif
 
+/*
+ * Don't call this in a row without the delay, otherwise it makes some of poor controllers
+ * overloaded and misses strokes. Recommended delay is 16ms.
+ *
+ * Thanks a lot, blargg! <http://geekhack.org/index.php?topic=14290.msg1068919#msg1068919>
+ */
 uint16_t adb_host_kbd_recv(void)
 {
     uint16_t data = 0;