certs: move scripts/check-blacklist-hashes.awk to certs/

This script is only used in certs/Makefile, so certs/ is a better
home for it.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>