sm: Fix issuer certificate look error due to legacy error code.
* sm/certchain.c (find_up): Get rid of the legacy return code -1 and chnage var name rc to err. (gpgsm_walk_cert_chain): Change var name rc to err. (do_validate_chain): Get rid of the legacy return code -1.
This was detected while fixing
- GnuPG-bug-id: T4757