ipip: fix a regression in ioctl

[ Upstream commit 3b7b514f44bff05d26a6499c4d4fac2a83938e6e ]

This is a regression introduced by
commit fd58156e (IPIP: Use ip-tunneling code.)

Similar to GRE tunnel, previously we only check the parameters
for SIOCADDTUNNEL and SIOCCHGTUNNEL, after that commit, the
check is moved for all commands.

So, just check for SIOCADDTUNNEL and SIOCCHGTUNNEL.

Also, the check for i_key, o_key etc. is suspicious too,
which did not exist before, reset them before passing
to ip_tunnel_ioctl().

Signed-off-by: Cong Wang <amwang@redhat.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>