As a workup action during disassociation, wpa_supplicant checks if the
disconnection could have been caused by PSK mismatch during WPA 4-way
handshake with function could_be_psk_mismatch() in event.c. A MSG_INFO
message will be sent on the control interface when there could be a PSK
mismatch, and this heuristic can be useful to indicate if the
disconnection is caused by a wrong passphrase provided by the user.
Here, propagate a new D-Bus signal 'PskMismatch' to notify other
applicantions.
Signed-off-by: Yichen Yu <yichenyu@chromium.org>