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