P2P : Fix for P2P group name

When device is in Chinese language, P2P group SSID names will be encoded
into UTF-8 hex format. When displaying group SSID in UI Settings, this
UTF-8 should be converted back to UTF-8 binary format.
Implemented method to convert UTF-8 hex to UTF-8 binary format. When
group is created, it checks the hex format by looking '\x' sequence,
then converts to binary format.

Change-Id: I381b9e6c89ea4c82d41d2d4b69effe0d5e71d2e8