WifiApConfigStore: validate the size of softap SSID with UTF-8 encode

String in Java will be converted to UTF-8 as the common HIDL type when
transported. And the length of the SSID information filed is also
allowed between 0 and 32 octets(bytes) that is followed by 802.11
standard document

Bug: 123109657
Test: unit test
Test: atest frameworks/opt/net/wifi/tests/wifitests
Change-Id: Id07c1063c651a22a046a40ff96392a07143db013
2 files changed