cifs: do not build smb1ops if legacy support is disabled

We should not be including unused SMB1/CIFS functions when legacy
support is disabled (CONFIG_CIFS_ALLOW_INSECURE_LEGACY turned
off), but especially obvious is not needing to build smb1ops.c
at all when legacy support is disabled. Over time we can move
more SMB1/CIFS and SMB2.0 legacy functions into ifdefs but this
is a good start (and shrinks the module size a few percent).

Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>