sound: Make keywest_driver static

I can't see any reason for struct i2c_driver keywest_driver to not be
static.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/ppc/keywest.c

@@ -98,7 +98,7 @@ static const struct i2c_device_id keywest_i2c_id[] = {
 	{ }
 };
 
-struct i2c_driver keywest_driver = {
+static struct i2c_driver keywest_driver = {
 	.driver = {
 		.name = "PMac Keywest Audio",
 	},