klippy: Introduce load_config_prefix() for modules that take parameters

Use both load_config() and load_config_prefix() functions when
dynamically loading a module from the extras directory - if the config
section name has parameters in it then use load_config_prefix().

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/heater_fan.py

@@ -33,5 +33,5 @@ class PrinterHeaterFan:
         self.fan.set_speed(print_time, power)
         return eventtime + 1.
 
-def load_config(config):
+def load_config_prefix(config):
     return PrinterHeaterFan(config)