drivers: cst816s: Clear the event buffer during a wake up

Currently with CST816S controllers (but not CST716S controllers) then a
swipe delivered whilst the device is asleep will sometimes be processed
after we wake it up. That's never likely to be useful. Fix this by
explicitly clearing the event buffer as part of the wakeup sequence.

Reported-by: Siroj42 <siroj42@users.noreply.github.com>
Fixes: #65
Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

wasp/drivers/cst816s.py

@@ -83,6 +83,7 @@ class CST816S:
         Just reset the chip in order to wake it up
         """
         self._reset()
+        self.event[0] = 0
 
     def sleep(self):
         """Put touch controller chip on sleep mode to save power.