accf_*.9: Rewrite broken synopsis

These manuals abused the name macro for every line of kernel cfg as well
as an example command to show the module name which was mixed in without
separation. This bugs the whatis database into thinking that INET and
kldload are names for this page, and violates best practice by mixing
commands and configuration in a continuous example.

Rewrite to use the kernel configuration macro, Cd, and show the module
name via an example configuration in rc.conf, according to the spec and
established practice. Do not bump the date because these markup errors
are not a content change.

MFC after: 3 days

(cherry picked from commit c59f12da11d75502b16f9163edc76514007462db)