Fix Wi-Fi QR code decode fail

ZXing generate QR code with default encoding ISO-8859-1,
the generated QR code is wrong encoded if there is a
character outside of the charset.

Generate QR code of UTF-8 encoding.

Bug: 131851854
Test: manual
Change-Id: I96a5e72a978c654b62d89b3b11dd3016bf0ee1df