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/freescale/mpc8315erdb/README b/board/freescale/mpc8315erdb/README
index b32132d..8ad6d81 100644
--- a/board/freescale/mpc8315erdb/README
+++ b/board/freescale/mpc8315erdb/README
@@ -63,7 +63,7 @@
 
 5.	Downloading and Flashing Images
 
-5.1	Reflash U-boot Image using U-boot
+5.1	Reflash U-Boot Image using U-Boot
 
 	NOR flash: