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/ls2080ardb/README b/board/freescale/ls2080ardb/README
index 7fc2569..6708ca9 100644
--- a/board/freescale/ls2080ardb/README
+++ b/board/freescale/ls2080ardb/README
@@ -87,7 +87,7 @@
 0x05_1000_0000 .. 0x05_FFFF_FFFF	IFC region #2
 0x80_8000_0000 .. 0xFF_FFFF_FFFF	DDR region #2
 
-Other addresses are either reserved, or not used directly by u-boot.
+Other addresses are either reserved, or not used directly by U-Boot.
 This list should be updated when more addresses are used.
 
 IFC region map from core's view