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/pci/oxygen/oxygen_io.c b/sound/pci/oxygen/oxygen_io.c
index 4b8a32c..c7851da 100644
--- a/sound/pci/oxygen/oxygen_io.c
+++ b/sound/pci/oxygen/oxygen_io.c
@@ -20,9 +20,9 @@
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/export.h>
+#include <linux/io.h>
 #include <sound/core.h>
 #include <sound/mpu401.h>
-#include <asm/io.h>
 #include "oxygen.h"
 
 u8 oxygen_read8(struct oxygen *chip, unsigned int reg)