netlabel: Remove unneeded in-kernel API functions

After some discussions with the Smack folks, well just Casey, I now have a
better idea of what Smack wants out of NetLabel in the future so I think it
is now safe to do some API "pruning".  If another LSM comes along that
needs this functionality we can always add it back in, but I don't see any
LSMs on the horizon which might make use of these functions.

Thanks to Rami Rosen who suggested removing netlbl_cfg_cipsov4_del() back
in February 2008.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Reviewed-by: James Morris <jmorris@namei.org>