net: ipv6: fix wrong ping_v6_sendmsg return value

[net-next commit fbfe80c8]

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

Bug: 9469865
CRs-Fixed: 573548
Change-Id: I82b7d3a37ba91ad24e6dbd97a4880745ce16ad31
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 68221869132d78d712d402efd53633ae8aebda20
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>