Update adafruit_74hc595.py

I didn't really understand what this was doing in the original code, but I thought I'd just keep it.

Co-authored-by: Scott Shawcroft <[email protected]>

Author: davidleedom

adafruit_74hc595.py

@@ -132,9 +132,7 @@ def gpio(self):
 
     @gpio.setter
     def gpio(self, val):
-
-        for x in range(0, self._number_of_shift_registers - 1):
-            self._gpio[x] = val[x] & 0xFF
+        self._gpio = val
 
         with self._device as spi:
             # pylint: disable=no-member