drivers/onewire: Enable pull-up when init'ing the 1-wire pin.

A previous version of the 1-wire driver (which was recently replaced by the
current one) had this behaviour and it allows to create a 1-wire bus
without any external pull-up resistors.

drivers/onewire/onewire.py

@@ -14,7 +14,7 @@ class OneWire:
 
     def __init__(self, pin):
         self.pin = pin
-        self.pin.init(pin.OPEN_DRAIN)
+        self.pin.init(pin.OPEN_DRAIN, pin.PULL_UP)
 
     def reset(self, required=False):
         reset = _ow.reset(self.pin)