net: ipv6: fix wrong ping_v6_sendmsg return value

net: ipv6: fix wrong ping_v6_sendmsg return value

ping_v6_sendmsg currently returns 0 on success. It should return
the number of bytes written instead.

Bug: 9469865
Bug 1412141

Change-Id: I14aad6018f0c3fd92dad315bc3ade04c0b3982e0
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 5f0fd6105f491b8b435863e98f7e96d617e3da84)
Reviewed-on: http://git-master/r/336272
(cherry picked from commit 6d931659abae7575ee64b16e3c2f3ee8bd350dd1)
Reviewed-on: http://git-master/r/351010
(cherry picked from commit 48c98b69c93e9b16cbdf5fdab18eaab07503ff8a)
Reviewed-on: http://git-master/r/390637
Reviewed-by: Jun Su <juns@nvidia.com>
Reviewed-by: Om Prakash Singh <omp@nvidia.com>
Reviewed-by: Liangcai Li <liangcail@nvidia.com>
Tested-by: Liangcai Li <liangcail@nvidia.com>
Reviewed-by: Manish Tuteja <mtuteja@nvidia.com>