Updated all examples to use the new/old usart_set_baudrate api.

examples/stm32/f4/stm32f4-discovery/usart/usart.c

@@ -35,7 +35,7 @@ void clock_setup(void)
 void usart_setup(void)
 {
 	/* Setup USART2 parameters. */
-	usart_set_baudrate(USART2, 38400, rcc_ppre1_frequency);
+	usart_set_baudrate(USART2, 38400);
 	usart_set_databits(USART2, 8);
 	usart_set_stopbits(USART2, USART_STOPBITS_1);
 	usart_set_mode(USART2, USART_MODE_TX);