Bug#822060: mention -R IP_address too

[積丹尼 Dan Jacobson <jidanni@jidanni.org>]

Package: openssh-client
Version: 1:7.2p2-4
File: /usr/share/man/man1/ssh-keygen.1.gz

      ssh-keygen -R hostname [-f known_hosts_file]
Say
      ssh-keygen -R hostname | IP_address [-f known_hosts_file]

     -R hostname
             Removes all keys belonging to hostname from a known_hosts file.
             This option is useful to delete hashed hosts (see the -H option
             above).

Say
     -R hostname | IP_address
             Removes all keys belonging to hostname or IP_address from a known_hosts file.
             This option is useful to delete hashed hosts (see the -H option
             above).

Also fix it ssh-keygen --help too.