net: mctp: take ownership of skb in mctp_local_output

In the Linux kernel, the following vulnerability has been resolved: net: mctp: take ownership of skb in mctp_local_output Currently, mctp_local_output only takes ownership of skb on success, and we may leak an skb if mctp_local_output fails in specific states; the skb ownership isn't transferred until the actual output routing occurs. Instead, make mctp_local_output free the skb on all error paths up to the route action, so it always consumes the passed skb.