wireless: brcmfmac: cfg80211: Fix check for ISO3166 code

The commit "regulatory: add NUL to request alpha2" increases the length of
alpha2 to 3. This causes a regression on brcmfmac, because
brcmf_cfg80211_reg_notifier() expect valid ISO3166 codes in the complete
array. So fix this accordingly.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c

@@ -6805,7 +6805,7 @@ static void brcmf_cfg80211_reg_notifier(struct wiphy *wiphy,
 		return;
 
 	/* ignore non-ISO3166 country codes */
-	for (i = 0; i < sizeof(req->alpha2); i++)
+	for (i = 0; i < 2; i++)
 		if (req->alpha2[i] < 'A' || req->alpha2[i] > 'Z') {
 			brcmf_err("not an ISO3166 code (0x%02x 0x%02x)\n",
 				  req->alpha2[0], req->alpha2[1]);