Update rpi_ws281x.py

fixed a typo missed an underscore!)

Author: boltar

library/rpi_ws281x/rpi_ws281x.py

@@ -111,7 +111,7 @@ def __init__(self, num, pin, freq_hz=800000, dma=10, invert=False,
     def _cleanup(self):
         # Clean up memory used by the library when not needed anymore.
         if self._leds is not None:
-            ws.ws2811_fini(self.leds)
+            ws.ws2811_fini(self._leds)
             ws.delete_ws2811_t(self._leds)
             self._leds = None
             self._channel = None