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/ppc/tumbler.c b/sound/ppc/tumbler.c
index 24c8766..c8fafba 100644
--- a/sound/ppc/tumbler.c
+++ b/sound/ppc/tumbler.c
@@ -32,8 +32,8 @@
 #include <linux/interrupt.h>
 #include <linux/string.h>
 #include <linux/of_irq.h>
+#include <linux/io.h>
 #include <sound/core.h>
-#include <asm/io.h>
 #include <asm/irq.h>
 #include <asm/machdep.h>
 #include <asm/pmac_feature.h>