Fix docstring typo to 'h(olding)' and 'i(nputs)'

Author: altendky

pymodbus/interfaces.py

@@ -180,7 +180,7 @@ def decode(self, fx):
         """ Converts the function code to the datastore to
 
         :param fx: The function we are working with
-        :returns: one of [d(iscretes),i(inputs),h(oliding),c(oils)
+        :returns: one of [d(iscretes),i(nputs),h(olding),c(oils)
         """
         return self.__fx_mapper[fx]