builtin/maintenance: fix typedef for function pointers

The typedefs for `maintenance_task_fn` and `maintenance_auto_fn` are
somewhat confusingly not true function pointers. As such, any user of
those typedefs needs to manually add the pointer to make use of them.

Fix this by making these true function pointers.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

builtin/gc.c

@@ -1533,20 +1533,20 @@ static int maintenance_task_incremental_repack(struct maintenance_run_opts *opts
 	return 0;
 }
 
-typedef int maintenance_task_fn(struct maintenance_run_opts *opts,
-				struct gc_config *cfg);
+typedef int (*maintenance_task_fn)(struct maintenance_run_opts *opts,
+				   struct gc_config *cfg);
 
 /*
  * An auto condition function returns 1 if the task should run
  * and 0 if the task should NOT run. See needs_to_gc() for an
  * example.
  */
-typedef int maintenance_auto_fn(struct gc_config *cfg);
+typedef int (*maintenance_auto_fn)(struct gc_config *cfg);
 
 struct maintenance_task {
 	const char *name;
-	maintenance_task_fn *fn;
-	maintenance_auto_fn *auto_condition;
+	maintenance_task_fn fn;
+	maintenance_auto_fn auto_condition;
 };
 
 static const struct maintenance_task tasks[] = {