nvmet-fc: sync header templates with comments

Comments were incorrect:
- defer_rcv was in host port template. moved to target port template
- Added Mandatory statements for target port template items

Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>