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: NStefan Wahren <stefan.wahren@i2se.com>
Acked-by: NFranky Lin <franky.lin@broadcom.com>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>