tty: serial: dz: include <linux/io.h> instead of <asm/io.h>

Include the more general linux/io.h instead of asm/io.h
as checkpatch suggests.
Signed-off-by: Zihao Tang <tangzihao1@hisilicon.com>
Signed-off-by: Jay Fang <f.fangjian@huawei.com>
Link: https://lore.kernel.org/r/1620874904-39285-3-git-send-email-f.fangjian@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/dz.c

@@ -47,8 +47,8 @@
 #include <linux/tty_flip.h>
 
 #include <linux/atomic.h>
+#include <linux/io.h>
 #include <asm/bootinfo.h>
-#include <asm/io.h>
 
 #include <asm/dec/interrupts.h>
 #include <asm/dec/kn01.h>