Support frontend status readiness query.

The caller could use it to check whether frontend status is ready to
read or not.

Bug: 171540820
Fix: 171540820
Test: atest android.media.tv.tuner.cts on AIDL and HILD HALs
Change-Id: I55610e02412d6043e7fab91d1a2bf187a8e5e3ba