devlink: Remove redundant free on error path

The current code performs unneeded free. Remove the redundant skb freeing
during the error path.

Fixes: 1555d204 ("devlink: Support for pipeline debug (dpipe)")
Signed-off-by: Arkadi Sharshevsky <arkadis@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>