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/SPI/README.ti_qspi_flash b/doc/SPI/README.ti_qspi_flash
index 1b86d01..9064739 100644
--- a/doc/SPI/README.ti_qspi_flash
+++ b/doc/SPI/README.ti_qspi_flash
@@ -1,4 +1,4 @@
-QSPI U-boot support
+QSPI U-Boot support
 ------------------
 
 Host processor is connected to serial flash device via qpsi
@@ -44,4 +44,4 @@
 Testing
 -------
 A seperated file named README.dra_qspi_test has been created which gives all the
-details about the commands required to test qspi at u-boot level.
+details about the commands required to test qspi at U-Boot level.