ipv6: correct the ipv6 option name - Pad0 to Pad1

The padding destination or hop-by-hop option is called Pad1 and not Pad0.

See RFC2460 (4.2) or the IANA ipv6-parameters registry:
http://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xml

Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: David S. Miller <davem@davemloft.net>