As the nvmet layer does not have the concept of a remoteport object, which
can be used to identify the entity on the other end of the fabric that is
to receive an LS, the hosthandle was introduced.  The driver passes the
hosthandle, a value representative of the remote port, with a ls request
receive. The LS request will create the association.  The transport will
remember the hosthandle for the association, and if there is a need to
initiate a LS request to the remote port for the association, the
hosthandle will be used. When the driver loses connectivity with the
remote port, it needs to notify the transport that the hosthandle is no
longer valid, allowing the transport to terminate associations related to
the hosthandle.

This patch adds support to the driver for the hosthandle. The driver will
use the ndlp pointer of the remote port for the hosthandle in calls to
nvmet_fc_rcv_ls_req().  The discovery engine is updated to invalidate the
hosthandle whenever connectivity with the remote port is lost.
Signed-off-by: Paul Ely <paul.ely@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>