ALSA: ppc: keywest: remove outdated comment

The I2C attach_adapter callback is gone. Remove this reference.
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Link: https://lore.kernel.org/r/20210310193227.333140-1-wsa@kernel.orgSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/ppc/keywest.c

@@ -13,12 +13,7 @@
 #include <sound/core.h>
 #include "pmac.h"
 
-/*
- * we have to keep a static variable here since i2c attach_adapter
- * callback cannot pass a private data.
- */
 static struct pmac_keywest *keywest_ctx;
-
 static bool keywest_probed;
 
 static int keywest_probe(struct i2c_client *client,