Use correct spelling of "U-Boot"

Correct spelling of "U-Boot" shall be used in all written text
(documentation, comments in source files etc.).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/board/blackvme/blackvme.c b/board/blackvme/blackvme.c
index eccdaf3..d8932ed 100644
--- a/board/blackvme/blackvme.c
+++ b/board/blackvme/blackvme.c
@@ -1,4 +1,4 @@
-/* U-boot - blackvme.c  board specific routines
+/* U-Boot - blackvme.c  board specific routines
  * (c) Wojtek Skulski 2010 info@skutek.com
  * Board info: http://www.skutek.com
  * Copyright (c) 2005-2009 Analog Devices Inc.