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/x86/cpu/resetvec.S b/arch/x86/cpu/resetvec.S
index 68a5b94..183275b 100644
--- a/arch/x86/cpu/resetvec.S
+++ b/arch/x86/cpu/resetvec.S
@@ -1,5 +1,5 @@
 /*
- *  U-boot - x86 Startup Code
+ *  U-Boot - x86 Startup Code
  *
  * (C) Copyright 2002
  * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
diff --git a/arch/x86/lib/bootm.c b/arch/x86/lib/bootm.c
index f441c84..783be69 100644
--- a/arch/x86/lib/bootm.c
+++ b/arch/x86/lib/bootm.c
@@ -162,7 +162,7 @@
 		* boot_params structure, and then jump to the kernel. We
 		* assume that %cs is 0x10, 4GB flat, and read/execute, and
 		* the data segments are 0x18, 4GB flat, and read/write.
-		* U-boot is setting them up that way for itself in
+		* U-Boot is setting them up that way for itself in
 		* arch/i386/cpu/cpu.c.
 		*
 		* Note that we cannot currently boot a kernel while running as