Fix an off-by-one error.

  I/SystemServer(  104): Wired Accessory Observer
  E/SystemServer(  104): Failure starting WiredAccessoryObserver
  E/SystemServer(  104): java.lang.ArrayIndexOutOfBoundsException: index=3 length=3
  E/SystemServer(  104): 	at com.android.server.WiredAccessoryObserver.<init>(WiredAccessoryObserver.java:79)
  E/SystemServer(  104): 	at com.android.server.ServerThread.run(SystemServer.java:401)

Change-Id: I6d40259d96b8c57c0ff04eab362a66b70e9fcd25