cifs: add new fields to cifs_ses to track requested security flavor

Currently we have the overrideSecFlg field, but it's quite cumbersome
to work with. Add some new fields that will eventually supercede it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

diff --cc fs/cifs/cifsfs.c
Simple merge

diff --cc fs/cifs/cifsglob.h
Simple merge

diff --cc fs/cifs/connect.c
Simple merge