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/lib/Kconfig b/lib/Kconfig
index 46d7034..c7eab46 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -16,7 +16,7 @@
 	depends on HAVE_PRIVATE_LIBGCC
 	help
 	  This option allows you to use the built-in libgcc implementation
-	  of U-boot instead of the one privided by the compiler.
+	  of U-Boot instead of the one privided by the compiler.
 	  If unsure, say N.
 
 config SYS_HZ