[wlan][sme] Improve key logging in Inspect

WLAN-1117 #done

Test: Verify Inspect output. Example:
```
4:
  @time = 80.777
  cipher = 00-0F-AC:4
  derived_key = PTK
5:
  @time = 80.777
  cipher = 00-0F-AC:2
  derived_key = GTK
  key_index = 2
```

Change-Id: Id1046dcfbd65fc800d6b7cfbd04e7dd7ee27052e