Fix minor typos in docs and comments.

drivers/input/ads7843e.c

@@ -595,7 +595,7 @@ static void ads7843e_worker(FAR void *arg)
     {
       /* If we have not yet processed the last pen up event, then we
        * cannot handle this pen down event. We will have to discard it.  That
-       * should be okay because we will set the timer to to sample again
+       * should be okay because we will set the timer to sample again
        * later.
        */