This reverts commit 64506929.

While the code does not actually break anything, it does not completely follow
RFC5214 yet. After talking back with Fred L. Templin, I agree that completing the
ISATAP specific RS/RA code, would pollute the kernel a lot with code that is better
implemented in userspace.

The kernel should not send RS packages for ISATAP at all.
Signed-off-by: NSascha Hlusiak <contact@saschahlusiak.de>
Acked-by: NFred L. Templin <Fred.L.Templin@boeing.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>