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/bf506f-ezkit/Makefile b/board/bf506f-ezkit/Makefile
index 0f134f9..7efe1bc 100644
--- a/board/bf506f-ezkit/Makefile
+++ b/board/bf506f-ezkit/Makefile
@@ -1,5 +1,5 @@
 #
-# U-boot - Makefile
+# U-Boot - Makefile
 #
 # Copyright (c) 2005-2008 Analog Device Inc.
 #
diff --git a/board/bf506f-ezkit/bf506f-ezkit.c b/board/bf506f-ezkit/bf506f-ezkit.c
index 638500d..77e40ae 100644
--- a/board/bf506f-ezkit/bf506f-ezkit.c
+++ b/board/bf506f-ezkit/bf506f-ezkit.c
@@ -1,5 +1,5 @@
 /*
- * U-boot - main board file
+ * U-Boot - main board file
  *
  * Copyright (c) 2008-2010 Analog Devices Inc.
  *