tty: serial: sb1250-duart: 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/1620874904-39285-13-git-send-email-f.fangjian@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sb1250-duart.c

@@ -34,7 +34,7 @@
 #include <linux/types.h>
 
 #include <linux/refcount.h>
-#include <asm/io.h>
+#include <linux/io.h>
 
 #include <asm/sibyte/sb1250.h>
 #include <asm/sibyte/sb1250_uart.h>