nvmet_fc: Clear SG list to avoid double frees

Clear SG list to avoid double frees of payload page list
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/target/fc.c

@@ -1624,6 +1624,8 @@ nvmet_fc_free_tgt_pgs(struct nvmet_fc_fcp_iod *fod)
 	for_each_sg(fod->data_sg, sg, fod->data_sg_cnt, count)
 		__free_page(sg_page(sg));
 	kfree(fod->data_sg);
+	fod->data_sg = NULL;
+	fod->data_sg_cnt = 0;
 }