regulatory: add NUL to alpha2

alpha2 is defined as 2-chars array, but is used in multiple
places as string (e.g. with nla_put_string calls), which
might leak kernel data.

Solve it by simply adding an extra char for the NULL
terminator, making such operations safe.

Cc: stable@vger.kernel.org
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

(cherry picked from commit a5fe8e76)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

include/net/regulatory.h

@@ -75,7 +75,7 @@ struct regulatory_request {
 	int wiphy_idx;
 	enum nl80211_reg_initiator initiator;
 	enum nl80211_user_reg_hint_type user_reg_hint_type;
-	char alpha2[2];
+	char alpha2[3];
 	u8 dfs_region;
 	bool intersect;
 	bool processed;