[ALSA] Stereo controls for M-Audio Revolution cards

This patch adds stereo controls to revo cards by making the ak4xxx
driver mixers configurable from the card driver.

Signed-off-by: Jani Alinikula <janialinikula@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

include/sound/ak4xxx-adda.h

@@ -53,6 +53,8 @@ struct snd_akm4xxx {
 		SND_AK4524, SND_AK4528, SND_AK4529,
 		SND_AK4355, SND_AK4358, SND_AK4381
 	} type;
+	unsigned int *num_stereo;			/* array of combined counts for the mixer */
+	char **channel_names;				/* array of mixer channel names */
 	struct snd_ak4xxx_ops ops;
 };