wifi: Add listen AP_EVENT_ENABLED event

The WPA_EVENT_CHANNEL_SWITCH only request to send it when channel
switch. It may not receive this event when hotspot started(It depends on
driver's design). Add listen AP_EVENT_ENABLED to handle if driver
doesn't support WPA_EVENT_CHANNEL_SWITCH when hotspot enabled.

Bug: 172536837
Test: Manual test to check behavior in log.
Change-Id: I8d97477da6b96bcd1ec3dbb9d5c560dc54f47bad
1 file changed