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/mmc/sh_sdhi.c b/drivers/mmc/sh_sdhi.c
index cc62c89..30e538c 100644
--- a/drivers/mmc/sh_sdhi.c
+++ b/drivers/mmc/sh_sdhi.c
@@ -526,7 +526,7 @@
 	opc = sh_sdhi_set_cmd(host, data, opc);
 
 	/*
-	 *  U-boot cannot use interrupt.
+	 *  U-Boot cannot use interrupt.
 	 *  So this flag may not be clear by timing
 	 */
 	sh_sdhi_writew(host, SDHI_INFO1, ~INFO1_RESP_END);