scsi: lpfc: Fix oops if nvmet_fc_register_targetport fails

if nvmet targetport registration fails, the driver encounters a NULL
pointer oops in lpfc_hb_timeout_handler.

To fix: if registration fails, ensure nvmet_support is cleared on the
port structure.

Also enhanced the log message on failure.

Cc: <stable@vger.kernel.org> # 4.12+
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>