global: Use proper project name U-Boot

Use proper project name in comments, Kconfig, readmes.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/0dbdf0432405c1c38ffca55703b6737a48219e79.1684307818.git.michal.simek@amd.com
diff --git a/doc/board/rockchip/rockchip.rst b/doc/board/rockchip/rockchip.rst
index 99376fb..4c555e1 100644
--- a/doc/board/rockchip/rockchip.rst
+++ b/doc/board/rockchip/rockchip.rst
@@ -333,12 +333,12 @@
 
 Unlike later SoC models the rk3066 BootROM doesn't have SDMMC support.
 If all other boot options fail then it enters into a BootROM mode on the USB OTG port.
-This method loads TPL/SPL on NAND with U-boot and kernel on SD card.
+This method loads TPL/SPL on NAND with U-Boot and kernel on SD card.
 
 SD Card
 ^^^^^^^
 
-U-boot expects a GPT partition map and a boot directory structure with files on the SD card.
+U-Boot expects a GPT partition map and a boot directory structure with files on the SD card.
 
 .. code-block:: none
 
@@ -363,7 +363,7 @@
         zImage
         rk3066a-mk808.dtb
 
-To write a U-boot image to the SD card (assumed to be /dev/sda):
+To write a U-Boot image to the SD card (assumed to be /dev/sda):
 
 .. code-block:: bash