brcmfmac: Fix check for ISO3166 code

BugLink: https://bugs.launchpad.net/bugs/1777063

commit 9b9322db upstream.

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.

Fixes: 657308f7 ("regulatory: add NUL to request alpha2")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[bwh: Backported to 4.4: adjust filename]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

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

@@ -6167,7 +6167,7 @@ static void brcmf_cfg80211_reg_notifier(struct wiphy *wiphy,
 		  req->alpha2[0], req->alpha2[1]);
 
 	/* 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 a ISO3166 code\n");
 			return;