Audio-hal: Fix VTS failures for display port.

Failure of VtsHalAudioV4_0Target#AudioPrimaryHidlTest.SetConnectedState(default).

VTS failure for Audio device AUX_DIGITAL if Audio HAL returns failure error.
This error in HAL occurs if it fails to query the display type. This test case
checks that HAL is notified of device connection/disconnection and should not
return any error even if no physical device is connected.

Do not return failure status when hal is not able to query the display port.

CRs-Fixed: 2292409
Change-Id: Ie86a359bf6ee15e7e3b06a4ab71695eb41642630