sched: Introduce sched_wake_tasks() function to wake up tasks

Add function to indicate when tasks need to be run.  This will allow
the scheduler code to know if there are any tasks that need to be
processed.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/avr/usbserial.c

@@ -42,8 +42,10 @@ static void
 console_pop_input(uint8_t len)
 {
     uint8_t needcopy = receive_pos - len;
-    if (needcopy)
+    if (needcopy) {
         memmove(receive_buf, &receive_buf[len], needcopy);
+        sched_wake_tasks();
+    }
     receive_pos = needcopy;
 }