ST7789.__init__.py small modifications

As discussed in: st7789/__init__.py suggestion for two small changes #22

Author: PaulskPt

library/ST7789/__init__.py

@@ -148,9 +148,8 @@ def __init__(self, port, cs, dc, backlight=None, rst=None, width=240,
 
         # Setup reset as output (if provided).
         if rst is not None:
-            GPIO.setup(rst, GPIO.OUT)
-
-        self.reset()
+            GPIO.setup(self._rst, GPIO.OUT)
+            self.reset()
         self._init()
 
     def send(self, data, is_data=True, chunk_size=4096):