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/doc/README.sata b/doc/README.sata
index d0ce667..b1104bb 100644
--- a/doc/README.sata
+++ b/doc/README.sata
@@ -1,4 +1,4 @@
-1. SATA usage in U-boot
+1. SATA usage in U-Boot
 
 	There are two ways to operate the hard disk
 
@@ -45,9 +45,9 @@
 	boot
 	=> bootm 200000 1000000 2000000
 
-1.3 How to load an image from an ext2 file system in U-boot?
+1.3 How to load an image from an ext2 file system in U-Boot?
 
-	U-boot doesn't support writing to an ext2 file system, so the
+	U-Boot doesn't support writing to an ext2 file system, so the
 	files must be written by other means (e.g. linux).
 
 	=> ext2ls sata 0:1 /