sh: dma-sysfs: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/20230313182918.1312597-16-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/sh/drivers/dma/dma-sysfs.c

@@ -45,13 +45,19 @@ static DEVICE_ATTR(devices, S_IRUGO, dma_show_devices, NULL);
 
 static int __init dma_subsys_init(void)
 {
+	struct device *dev_root;
 	int ret;
 
 	ret = subsys_system_register(&dma_subsys, NULL);
 	if (unlikely(ret))
 		return ret;
 
-	return device_create_file(dma_subsys.dev_root, &dev_attr_devices);
+	dev_root = bus_get_dev_root(&dma_subsys);
+	if (dev_root) {
+		ret = device_create_file(dev_root, &dev_attr_devices);
+		put_device(dev_root);
+	}
+	return ret;
 }
 postcore_initcall(dma_subsys_init);