target/tcm_fc: use CPU affinity for responses

The libfc stack assigns exchange IDs based on the CPU the request
was received on, so we need to send the responses via the same CPU.
Otherwise the send logic gets confuses and responses will be delayed,
causing exchange timeouts on the initiator side.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Cc: stable@vger.kernel.org # 4.5+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>