brcmfmac: use brcmf_get_ifp() to map ifidx to struct brcmf_if instance

The knowledge on how to map the interface index to a struct brcmf_if
instance is in brcmf_get_ifp() so use that function when only the
interface index is known instead of accessing brcmf_pub::iflist
directly.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
diff --git a/drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c
index 0c29bf6..cee9ff4 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c
@@ -6213,7 +6213,7 @@
 struct brcmf_cfg80211_info *brcmf_cfg80211_attach(struct brcmf_pub *drvr,
 						  struct device *busdev)
 {
-	struct net_device *ndev = drvr->iflist[0]->ndev;
+	struct net_device *ndev = brcmf_get_ifp(drvr, 0)->ndev;
 	struct brcmf_cfg80211_info *cfg;
 	struct wiphy *wiphy;
 	struct brcmf_cfg80211_vif *vif;