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/include/configs/vexpress_ca9x4.h b/include/configs/vexpress_ca9x4.h
index 71233d8..99be50a 100644
--- a/include/configs/vexpress_ca9x4.h
+++ b/include/configs/vexpress_ca9x4.h
@@ -12,7 +12,7 @@
 #define __VEXPRESS_CA9X4_H
 
 #define CONFIG_VEXPRESS_ORIGINAL_MEMORY_MAP
-#define CONFIG_BOOTP_VCI_STRING     "U-boot.armv7.vexpress_ca9x4"
+#define CONFIG_BOOTP_VCI_STRING     "U-Boot.armv7.vexpress_ca9x4"
 #include "vexpress_common.h"
 
 #endif /* VEXPRESS_CA9X4_H */