stm32f4: add serial print port

Add the stm32F4 board's serial ports support.
User can use it easily.
The user only need to edit the number of the usart.
The patch also fix the serial print out.

Last, this version of patch fix the first patch checkpatch.pl error.
Thanks to Kamil Lulko.

Signed-off-by: kunhuahuang <huangkunhua@gmail.com>
diff --git a/include/configs/stm32f429-discovery.h b/include/configs/stm32f429-discovery.h
index 7f569fd..84cc19d 100644
--- a/include/configs/stm32f429-discovery.h
+++ b/include/configs/stm32f429-discovery.h
@@ -50,8 +50,14 @@
 
 #define CONFIG_STM32_GPIO
 #define CONFIG_STM32_SERIAL
-
-#define CONFIG_STM32_USART1
+/*
+ * Configuration of the USART
+ * 1:   TX:PA9  PX:PA10
+ * 2:   TX:PD5  RX:PD6
+ * 3:   TX:PC10 RX:PC11
+ * 6:   TX:PC6  RX:PC7
+ */
+#define CONFIG_STM32_USART		1
 
 #define CONFIG_STM32_HSE_HZ		8000000