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/arch/microblaze/lib/muldi3.c b/arch/microblaze/lib/muldi3.c
index 5c1a154..95b6b32 100644
--- a/arch/microblaze/lib/muldi3.c
+++ b/arch/microblaze/lib/muldi3.c
@@ -1,5 +1,5 @@
 /*
- * U-boot - muldi3.c contains routines for mult and div
+ * U-Boot - muldi3.c contains routines for mult and div
  *
  *
  * SPDX-License-Identifier:	GPL-2.0+