soc: sunxi: mbus: don't access of_root directly

Don't access of_root directly as it reduces the build test coverage for
this driver with COMPILE_TEST=y and OF=n. Use existing helper functions
to retrieve the relevant information.

Suggested-by: Rob Herring <[e-mail]>
Acked-by: Jernej Skrabec <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/soc/sunxi/sunxi_mbus.c

···
 
 static int __init sunxi_mbus_init(void)
 {
-	if (!of_device_compatible_match(of_root, sunxi_mbus_platforms))
+	if (!of_machine_compatible_match(sunxi_mbus_platforms))
 		return 0;
 
 	bus_register_notifier(&platform_bus_type, &sunxi_mbus_nb);