documentation update - remove old out of date feature info

Following up on a suggestion by Matthew Wilcox ...

The cifs CHANGES documentation file is out of date, and more
current information is in the wiki.  Delete the old version
information that is of little use to make this documentation
file more readable.

CC: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>