download/u-boot: Prepare files per board instead of per revision

The U-Boot download script is designed to help with releasing
u-boot-libre and it can only prepare a generic U-Boot v2021.07 tree.
However, we will need to build board-specific versions of U-Boot to be
able to use it as a coreboot payload effectively.

As a first step toward that, make the download script prepare per-board
copies of U-Boot v2021.07. Then, add a 'v2021.07' pseudo-board for the
u-boot-libre release script to work on.

The u-boot-libre deblob script hash ends up chaning due to copying my
author attribution from the download script, update its hash.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

resources/scripts/build/release/u-boot-libre

@@ -102,7 +102,7 @@ release_deblobbed_uboot()
 	   "${tarball}.xz"
 
 	mkdir -p "$(dirname ${tmpdir})"
-	cp -R "u-boot/u-boot/" "${tmpdir}"
+	cp -R "u-boot/v${version}/" "${tmpdir}"
 
 	rm -rf ${tmpdir}/.git ${tmpdir}/.gitignore
 	make -C ${tmpdir} distclean