dm: serial: Reset the watchdog while waiting in getc()

We have moved the busy-wait loop out of drivers and into the uclass. This
means that we must reset the watchdog when busy-waiting.

Note: some drivers may still have a busy-wait even with driver model, as
a transition mechanism. Driver model will tolerate this, and is can be
cleaned up when all users of the driver use driver model. An example is
ns16550.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>

drivers/serial/serial-uclass.c

@@ -11,9 +11,12 @@
 #include <os.h>
 #include <serial.h>
 #include <stdio_dev.h>
+#include <watchdog.h>
 #include <dm/lists.h>
 #include <dm/device-internal.h>
 
+#include <ns16550.h>
+
 DECLARE_GLOBAL_DATA_PTR;
 
 /* The currently-selected console serial device */
@@ -119,6 +122,8 @@ static int serial_getc_dev(struct udevice *dev)
 
 	do {
 		err = ops->getc(dev);
+		if (err == -EAGAIN)
+			WATCHDOG_RESET();
 	} while (err == -EAGAIN);
 
 	return err >= 0 ? err : 0;