ALSA: ac97c: constify ac97_pcm structures

ac97_pcm are not supposed to change at runtime. All functions
working with ac97_pcm provided by <sound/ac97_codec.h> work with
const ac97_pcm. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/atmel/ac97c.c

@@ -558,7 +558,7 @@ static irqreturn_t atmel_ac97c_interrupt(int irq, void *dev)
 	return retval;
 }
 
-static struct ac97_pcm at91_ac97_pcm_defs[] = {
+static const struct ac97_pcm at91_ac97_pcm_defs[] = {
 	/* Playback */
 	{
 		.exclusive = 1,