xen/xenbus: Fix a double free in xenbus_map_ring_pv()

When there is an error the caller frees "info->node" so the free here
will result in a double free.  We should just delete first kfree().

Fixes: 3848e4e ("xen/xenbus: avoid large structs and arrays on the stack")
Signed-off-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/r/20200710113610.GA92345@mwanda
Reviewed-by: Juergen Gross <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>

Author: Dan Carpenter

drivers/xen/xenbus/xenbus_client.c

@@ -693,10 +693,8 @@ static int xenbus_map_ring_pv(struct xenbus_device *dev,
 	bool leaked;
 
 	area = alloc_vm_area(XEN_PAGE_SIZE * nr_grefs, info->ptes);
-	if (!area) {
-		kfree(node);
+	if (!area)
 		return -ENOMEM;
-	}
 
 	for (i = 0; i < nr_grefs; i++)
 		info->phys_addrs[i] =