audio: Use get_audio_port_v7 in the default wrapper

get_audio_port_v7 interface method was added in aosp/1518624
but wasn't used in the default wrapper due to the refactoring
ongoing at that time. Fixing this omission.

Bug: 160352965
Test: atest VtsHalAudioV7_0TargetTest
Change-Id: I1e3594f30fe8fa319d0b5b4244531c9142870503
Merged-In: I1e3594f30fe8fa319d0b5b4244531c9142870503