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/tools/patman/README b/tools/patman/README
index 5bd74c4..e36857d 100644
--- a/tools/patman/README
+++ b/tools/patman/README
@@ -138,7 +138,7 @@
 How to install it
 =================
 
-The most up to date version of patman can be found in the U-boot sources.
+The most up to date version of patman can be found in the U-Boot sources.
 However to use it on other projects it may be more convenient to install it as
 a standalone application. A distutils installer is included, this can be used
 to install patman: