ALSA: hda: readl/writel need linux/io.h

Fixes: 19abfefd ("ALSA: hda: Direct MMIO accesses")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/hda/hdac_bus.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/io.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/export.h>