Don't complain about documented symbols with find-doc-nits -d -o

Don't complain about documented symbols with find-doc-nits -d -o

find-doc-nits can give a list of symbols that were added since 1.1.1 and
are undocumented (using -o). To do this it uses the missingcrypto111.txt
and missingssl111.txt files which give a snapshot of the undocumented
symbols at the time of the 1.1.1 release. Currently it complains about
symbols that are in those files that have subsequently been documented.
This isn't particularly helpful so we suppress that feature when "-o"
is being used.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10981)