openvswitch: Use correct type while allocating flex array.

Flex array is used to allocate hash buckets which is type struct
hlist_head, but we use `struct hlist_head *` to calculate
array size.  Since hlist_head is of size pointer it works fine.

Following patch use correct type.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 5c519b1..1aa84dc 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -240,7 +240,7 @@
 	struct flex_array *buckets;
 	int i, err;
 
-	buckets = flex_array_alloc(sizeof(struct hlist_head *),
+	buckets = flex_array_alloc(sizeof(struct hlist_head),
 				   n_buckets, GFP_KERNEL);
 	if (!buckets)
 		return NULL;