Update U-Boot's build timestamp on every compile

Use the GNU 'date' command to auto-generate a new U-Boot
timestamp on every compile.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/board/lwmon/lwmon.c b/board/lwmon/lwmon.c
index d062466..878752c 100644
--- a/board/lwmon/lwmon.c
+++ b/board/lwmon/lwmon.c
@@ -762,12 +762,13 @@
 #ifdef CONFIG_LCD_INFO
 #include <lcd.h>
 #include <version.h>
+#include <timestamp.h>
 
 void lcd_show_board_info(void)
 {
 	char temp[32];
 
-	lcd_printf ("%s (%s - %s)\n", U_BOOT_VERSION, __DATE__, __TIME__);
+	lcd_printf ("%s (%s - %s)\n", U_BOOT_VERSION, U_BOOT_DATE, U_BOOT_TIME);
 	lcd_printf ("(C) 2008 DENX Software Engineering GmbH\n");
 	lcd_printf ("    Wolfgang DENK, wd@denx.de\n");
 #ifdef CONFIG_LCD_INFO_BELOW_LOGO