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/drivers/soc/Makefile b/drivers/soc/Makefile
index 99345eb..69f680c 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -1,5 +1,5 @@
 #
-# Makefile for the U-boot SOC specific device drivers.
+# Makefile for the U-Boot SOC specific device drivers.
 #
 # SPDX-License-Identifier:	GPL-2.0+
 #