boot: Call flush() before booting

In a lot of cases kernel resets UART HW. To ensure that U-Boot messages
printed before booting the kernel are not lost, call new U-Boot console
flush() function.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd/boot.c

@@ -32,6 +32,7 @@ static int do_go(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	addr = hextoul(argv[1], NULL);
 
 	printf ("## Starting application at 0x%08lX ...\n", addr);
+	flush();
 
 	/*
 	 * pass address parameter as argv[0] (aka command name),