[Wi-Fi] Fix EntityHeader signal strength icon invisible problem

WifiDetailPreferenceController2#onUpdated() triggers each controller
to displayPreference(PreferenceScreen screen) for visibility
updating. However, WifiDetailPreferenceController2 is a much
complex controller which should controll it's components visibility
by itself.

Bug: 152886237
Test: manual visual
      Observe EntityHeader signal strength icon UI display.
Change-Id: I80a8341ae051f21410070a81e01716eb49d2c8da