ALSA: use linux/io.h to fix compile warnings

For helping to reduce Greert's regression list...
  src/sound/drivers/mtpav.c: error: implicit declaration of function 'inb'
  src/sound/drivers/mtpav.c: error: implicit declaration of function 'outb'
  ...

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/drivers/mtpav.c b/sound/drivers/mtpav.c
index da03597..5c426df 100644
--- a/sound/drivers/mtpav.c
+++ b/sound/drivers/mtpav.c
@@ -55,14 +55,13 @@
 #include <linux/err.h>
 #include <linux/platform_device.h>
 #include <linux/ioport.h>
+#include <linux/io.h>
 #include <linux/moduleparam.h>
 #include <sound/core.h>
 #include <sound/initval.h>
 #include <sound/rawmidi.h>
 #include <linux/delay.h>
 
-#include <asm/io.h>
-
 /*
  *      globals
  */