serial: mfd: Add nmi_touch_watchdog() into the console write function

This is following what 8250 driver is doing in console write function,
to avoid the hardware lockup case.

v2: incldudes the <linux/nmi.h>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/mfd.c

@@ -36,6 +36,7 @@
 #include <linux/serial_mfd.h>
 #include <linux/dma-mapping.h>
 #include <linux/pci.h>
+#include <linux/nmi.h>
 #include <linux/io.h>
 #include <linux/debugfs.h>
 #include <linux/pm_runtime.h>
@@ -1113,6 +1114,8 @@ serial_hsu_console_write(struct console *co, const char *s, unsigned int count)
 	unsigned int ier;
 	int locked = 1;
 
+	touch_nmi_watchdog();
+
 	local_irq_save(flags);
 	if (up->port.sysrq)
 		locked = 0;