Fix Coverity 1201740 & 1201712: uninitialised values

Fix Coverity 1201740 & 1201712: uninitialised values

These are both false positives since the `d` array is initialised by
the `DES_cfb_encrypt()` call via the `l2cn` macro.  Rather than ignoring them
and having them crop up later, it's easier to just add an initialiser.

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/17894)