certs/blacklist: fix kernel doc interface issue

certs/blacklist.c:84: warning: Function parameter or member 'hash' not
described in 'mark_hash_blacklisted'

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ben Boeckel <mathstuf@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: keyrings@vger.kernel.org
Cc: linux-kernel@vger.kernel.org