Wifi usability: Add trigger type of Wifi unusable events into stats collection

Bug: 113262380

Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh

Change-Id: Iaafe171adefcb9aa49c11d4d2cb91dd4744efa76
Signed-off-by: Mingguang Xu <mingguangxu@google.com>
6 files changed