wifi: Support for AP with Chinese GBK Charset SSID

It doesn't support Chinese GBK Charset in original android.
But there are some APs with Chinese GBK Charset SSID, it will result
in that wifi can't display these APs nomally and connect to these APs.
Here make a conversion in wifi JNI layer. When "SCAN" or "GET_NETWORK"
command has the reply with Chinese GBK Charset SSID, convert GBK to UTF-8.

CRs-Fixed: 497995
Change-Id: If4d1d5bc3a98490db55c69ebcc0c78d526b7a563

Wifi: get rid of the log from Gbk2Utf

In android_net_wifi_Gbk2Utf.cpp, we set DBG as true,
this should be false in default.

Change-Id: Ib5673f0817677887d6b050191d96edb33fdb8799
CRs-Fixed: 690860