scripts: download: u-boot: fix u-boot repository URL

Without that fix we have the following warning during the download:
    Cloning into 'u-boot/u-boot'...
    warning: redirecting to https://source.denx.de/u-boot/u-boot.git/



Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>

resources/scripts/download/u-boot

@@ -65,7 +65,7 @@ downloadfor() {
 
 	if [ ! -d "${uboot_dir}" ]; then
 		printf "Download u-boot from upstream:\n"
-		git clone https://source.denx.de/u-boot/u-boot \
+		git clone https://source.denx.de/u-boot/u-boot.git \
 		    "${uboot_dir}" || \
 		    rm -Rf "${uboot_dir}"
 		if [ ! -d "${uboot_dir}" ]; then