[CIFS] Re-enable Lanman security

commit ac68392460ffefed13020967bae04edc4d3add06 ("[CIFS] Allow raw
ntlmssp code to be enabled with sec=ntlmssp") added a new bit to the
allowed security flags mask but seems to have inadvertently removed
Lanman security from the allowed flags. Add it back.

CC: Stable <stable@kernel.org>
Signed-off-by: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>