[ Upstream commit a6f79d0f ]

PPPoL2TP sockets should comply with the standard send*() return values
(i.e. return number of bytes sent instead of 0 upon success).
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>