regmap: destroy mutex (if used) in regmap_exit()

While not destroying mutexes doesn't lead to memory leaks, it's still
the correct thing to do for mutex debugging accounting.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20200928120614.23172-1-brgl@bgdev.plSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap.c

@@ -1370,6 +1370,8 @@ void regmap_exit(struct regmap *map)
 	}
 	if (map->hwlock)
 		hwspin_lock_free(map->hwlock);
+	if (map->lock == regmap_lock_mutex)
+		mutex_destroy(&map->mutex);
 	kfree_const(map->name);
 	kfree(map->patch);
 	kfree(map);