Bluetooth: btuart_cs: remove obsolete header

Use <linux/io.h> instead of <asm/io.h>, fixes checkpatch
Warning;

Signed-off-by: Prasanna Karthik <mkarthi3@visteon.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/bluetooth/btuart_cs.c b/drivers/bluetooth/btuart_cs.c
index dfaa1c9..4c001a8 100644
--- a/drivers/bluetooth/btuart_cs.c
+++ b/drivers/bluetooth/btuart_cs.c
@@ -38,7 +38,7 @@
 #include <linux/serial.h>
 #include <linux/serial_reg.h>
 #include <linux/bitops.h>
-#include <asm/io.h>
+#include <linux/io.h>
 
 #include <pcmcia/cistpl.h>
 #include <pcmcia/ciscode.h>