Documentation/auxiliary_bus: Add example code for module_auxiliary_driver()

Add an example code snipit to the module_auxiliary_driver()
documentation which is consistent with the other example code in the
elsewhere in the documentation.
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20211202044305.4006853-6-ira.weiny@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/auxiliary_bus.h

@@ -66,6 +66,10 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv);
  * Helper macro for auxiliary drivers which do not do anything special in
  * module init/exit. This eliminates a lot of boilerplate. Each module may only
  * use this macro once, and calling it replaces module_init() and module_exit()
+ *
+ * .. code-block:: c
+ *
+ *	module_auxiliary_driver(my_drv);
  */
 #define module_auxiliary_driver(__auxiliary_driver) \
 	module_driver(__auxiliary_driver, auxiliary_driver_register, auxiliary_driver_unregister)