ns16550: Add WATCHDOG_RESET to putc for short watchdog timeout boards

Call watchdog_reset() upon newline. This is done here in putc
since the environment code uses a single puts() to print the complete
envrironment upon "printenv". So we can't put this watchdog call
in puts().

This is needed for boards with a very short watchdog timeout, like the
lwmon5 with a 100ms timeout. Without this patch this board resets in the
commands with long outputs, like "printenv" or "fdt print".

Note that the image size is not increased with this patch when
CONFIG_HW_WATCHDOG or CONFIG_WATCHDOG are not defined since the compiler
optimizes this additional code away.

Signed-off-by: Stefan Roese <sr@denx.de>

Fix typo in comment.
Signed-off-by: Wolfgang Denk <wd@denx.de>

drivers/serial/ns16550.c

@@ -70,6 +70,15 @@ void NS16550_putc (NS16550_t com_port, char c)
 {
 	while ((serial_in(&com_port->lsr) & UART_LSR_THRE) == 0);
 	serial_out(c, &com_port->thr);
+
+	/*
+	 * Call watchdog_reset() upon newline. This is done here in putc
+	 * since the environment code uses a single puts() to print the complete
+	 * environment upon "printenv". So we can't put this watchdog call
+	 * in puts().
+	 */
+	if (c == '\n')
+		WATCHDOG_RESET();
 }
 
 #ifndef CONFIG_NS16550_MIN_FUNCTIONS