ALSA: Include linux/io.h instead of asm/io.h

Nowadays it's recommended.  Replace all in a shot.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/isa/azt2320.c b/sound/isa/azt2320.c
index b8e768e..fff186f 100644
--- a/sound/isa/azt2320.c
+++ b/sound/isa/azt2320.c
@@ -29,7 +29,7 @@
     activation method (full-duplex audio!).
 */
 
-#include <asm/io.h>
+#include <linux/io.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/time.h>