init _BUFF - one line code

Author: Bongjun Hur

adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py

@@ -127,9 +127,9 @@ def send_dhcp_message(self, state, time_elapsed):
         :param float time_elapsed: Number of seconds elapsed since renewal.
 
         """
-        # before making send packet, shoule init _BUFF. if not, DHCP sometimes fails, wrong padding, garbage bytes, ...
-        for i in range(len(_BUFF)):
-            _BUFF[i] = 0
+        # before making send packet, shoule init _BUFF. 
+        # if not, DHCP sometimes fails, wrong padding, garbage bytes, ...
+        _BUFF[:] = b'\x00' * len(_BUFF)
 
         # OP
         _BUFF[0] = DHCP_BOOT_REQUEST