ALSA: aoa: make soundbus_bus_type const

Since commit d492cc25 ("driver core: device.h: make struct
bus_type a const *"), the driver core can properly handle constant
struct bus_type, move the soundbus_bus_type variable to be a constant
structure as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240214-bus_cleanup-alsa-v1-1-8fedbb4afa94@marliere.netSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/aoa/soundbus/core.c

@@ -127,7 +127,7 @@ static void soundbus_device_shutdown(struct device *dev)
 
 /* soundbus_dev_attrs is declared in sysfs.c */
 ATTRIBUTE_GROUPS(soundbus_dev);
-static struct bus_type soundbus_bus_type = {
+static const struct bus_type soundbus_bus_type = {
 	.name		= "aoa-soundbus",
 	.probe		= soundbus_probe,
 	.uevent		= soundbus_uevent,