[SCSI] libfc: Handle unsolicited PRLO request

Resubmitting after incorporating Joe's review comment.

Unsolicited PRLO request is now handled by sending LS_ACC,
and then relogin to the remote port if an N-port login
session exists for that remote port.

Note that this patch should be applied on top of Joe Eykholt's
"Fix remote port restart problem" patch.

Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>