wifi: Add bssid in SoftApInfo

Support API: get current AP macaddress since
current AP macaddress might be ramdomized.

Bug: 151189102
Test: atest frameworks/base/wifi/tests
Change-Id: If3907521e4c98738480ed58d209e567f618466c9
diff --git a/wifi/api/system-current.txt b/wifi/api/system-current.txt
index e96365b..9cfa256 100644
--- a/wifi/api/system-current.txt
+++ b/wifi/api/system-current.txt
@@ -285,6 +285,7 @@
   public final class SoftApInfo implements android.os.Parcelable {
     method public int describeContents();
     method public int getBandwidth();
+    method @Nullable public android.net.MacAddress getBssid();
     method public int getFrequency();
     method public void writeToParcel(@NonNull android.os.Parcel, int);
     field public static final int CHANNEL_WIDTH_160MHZ = 6; // 0x6