brcmfmac: obtain ifp through wdev structure

For P2P_DEVICE interface the function brcmf_cfg80211_update_proto_addr_mode()
resulted in a crash, because it assumed wdev->netdev would be valid. The
ifp should be obtained through the driver vif structure which contains the
wireless_dev.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c

@@ -497,8 +497,11 @@ brcmf_configure_arp_offload(struct brcmf_if *ifp, bool enable)
 static void
 brcmf_cfg80211_update_proto_addr_mode(struct wireless_dev *wdev)
 {
-	struct net_device *ndev = wdev->netdev;
-	struct brcmf_if *ifp = netdev_priv(ndev);
+	struct brcmf_cfg80211_vif *vif;
+	struct brcmf_if *ifp;
+
+	vif = container_of(wdev, struct brcmf_cfg80211_vif, wdev);
+	ifp = vif->ifp;
 
 	if ((wdev->iftype == NL80211_IFTYPE_ADHOC) ||
 	    (wdev->iftype == NL80211_IFTYPE_AP) ||