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/block/mvsata_ide.c b/drivers/block/mvsata_ide.c
index 2c6d424..7b6a155 100644
--- a/drivers/block/mvsata_ide.c
+++ b/drivers/block/mvsata_ide.c
@@ -83,7 +83,7 @@
  * Status codes to return to client callers. Currently, callers ignore
  * exact value and only care for zero or nonzero, so no need to make this
  * public, it is only #define'd for clarity.
- * If/when standard negative codes are implemented in U-boot, then these
+ * If/when standard negative codes are implemented in U-Boot, then these
  * #defines should be moved to, or replaced by ones from, the common list
  * of status codes.
  */