openvswitch: avoid warnings in vport_from_priv

This change, firstly, avoids declaring the formal parameter const,
since it is treated as non const. (to avoid -Wcast-qual)
Secondly, it cast the pointer from void* to u8*, since it is used
in arithmetic (to avoid -Wpointer-arith)
Signed-off-by: Daniele Di Proietto <daniele.di.proietto@gmail.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

net/openvswitch/vport.h

@@ -185,9 +185,9 @@ static inline void *vport_priv(const struct vport *vport)
  * the result of a hash table lookup.  @priv must point to the start of the
  * private data area.
  */
-static inline struct vport *vport_from_priv(const void *priv)
+static inline struct vport *vport_from_priv(void *priv)
 {
-	return (struct vport *)(priv - ALIGN(sizeof(struct vport), VPORT_ALIGN));
+	return (struct vport *)((u8 *)priv - ALIGN(sizeof(struct vport), VPORT_ALIGN));
 }
 
 void ovs_vport_receive(struct vport *, struct sk_buff *,