qcacld-3.0: Make hdd_ipa_forward() static

Recently change "qcacld-3.0: ipa exception packet forwarding crash
fix" introduced new code including function hdd_ipa_forward().  This
function is only accessed from within wlan_hdd_ipa.c so it should have
been made static, however it wasn't. And in addition a public
protototype was not defined. This causes a build failure when the
-Wmissing-prototypes switch is used.  To fix this issue make
hdd_ipa_forward() static.

Change-Id: I8432ab734a0305f3d515a17ef324c7f8f60c0ba0
CRs-Fixed: 1080027

core/hdd/src/wlan_hdd_ipa.c

@@ -2526,8 +2526,8 @@ static void hdd_ipa_send_skb_to_network(qdf_nbuf_t skb,
  *
  * Return: None
  */
-void hdd_ipa_forward(struct hdd_ipa_priv *hdd_ipa,
-		hdd_adapter_t *adapter, qdf_nbuf_t skb)
+static void hdd_ipa_forward(struct hdd_ipa_priv *hdd_ipa,
+			    hdd_adapter_t *adapter, qdf_nbuf_t skb)
 {
 	qdf_nbuf_t copy;
 	struct hdd_ipa_pm_tx_cb *pm_tx_cb;