iscsi-target: avoid NULL pointer in iscsi_copy_param_list failure

In iscsi_copy_param_list() a failed iscsi_param_list memory allocation
currently invokes iscsi_release_param_list() to cleanup, and will promptly
trigger a NULL pointer dereference.

Instead, go ahead and return for the first iscsi_copy_param_list()
failure case.

Found by coverity.
Signed-off-by: NJoern Engel <joern@logfs.org>
Cc: <stable@vger.kernel.org> # v3.1+
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target_parameters.c

@@ -601,7 +601,7 @@ int iscsi_copy_param_list(
 	param_list = kzalloc(sizeof(struct iscsi_param_list), GFP_KERNEL);
 	if (!param_list) {
 		pr_err("Unable to allocate memory for struct iscsi_param_list.\n");
-		goto err_out;
+		return -1;
 	}
 	INIT_LIST_HEAD(&param_list->param_list);
 	INIT_LIST_HEAD(&param_list->extra_response_list);