databases/db18: Fix linking problem about OpenSSL

Fix the problem that OpenSSL in base system is linked even if
'DEFAULT_VERSIONS=ssl=openssl' is specified in make.conf.

While I'm here,

• Pet portlint and portclippy.
• Tidy up Makefile with portfmt.

PR: 264520
MFH: 2022Q3
(cherry picked from commit 043c4ce17d47717559aeb567b04d1913ec0626b6)