[RTNETLINK]: Possible dereference in net/core/rtnetlink.c

another possible dereference spotted by coverity (#cid 1390).
if the nlmsg_parse() call fails, we goto errout, where we call
dev_put(), with dev still initialized to NULL.

Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>