libaudiohal: Align use of get_audio_port_v7 with default wrapper

Use the same logic when calling get_audio_port_v7
as the default wrapper, with separation for pre-V7
and V7 versions of the code.

Bug: 160352965
Test: check audio on device
      also, use a modified APM config with USB Audio on 'usb' module
Change-Id: I5a6e2164b43d086aec6ffad5300edbade04cca1f