ALSA: Allow passing platform_data for pxa2xx-ac97

This patch adds support for passing platform data to ac97 bus devices
from PXA2xx-AC97 driver..

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/include/sound/ac97_codec.h b/include/sound/ac97_codec.h
index 9b1c098..3dae3f7 100644
--- a/include/sound/ac97_codec.h
+++ b/include/sound/ac97_codec.h
@@ -32,6 +32,9 @@
 #include "control.h"
 #include "info.h"
 
+/* maximum number of devices on the AC97 bus */
+#define	AC97_BUS_MAX_DEVICES	4
+
 /*
  *  AC'97 codec registers
  */