debug_uart: Add CR before and after announce string

Add linefeeds before and after the announce string. This makes the
output easier to read, especially if some text follows the announce
message without a specific additional CR.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/debug_uart.h

@@ -112,7 +112,7 @@ void printhex8(unsigned int value);
 void printdec(unsigned int value);
 
 #ifdef CONFIG_DEBUG_UART_ANNOUNCE
-#define _DEBUG_UART_ANNOUNCE	printascii("<debug_uart> ");
+#define _DEBUG_UART_ANNOUNCE	printascii("\n<debug_uart>\n");
 #else
 #define _DEBUG_UART_ANNOUNCE
 #endif