cypress-nvram: disassociate from external source repo

cypress-nvram: disassociate from external source repo

Since all NVRAM files in external repo are now upstreamed and to lower
future maintenance cost, disassociate the package from external source
repo.

All upstream pending NVRAM files shall be stored locally from now on.

Signed-off-by: Kuan-Yi Li <kyli@abysm.org>
[Remove outdated URL, add SPDX-License-Identifier]
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>