Propagate AudioFlinger open output flags to audio policy

Returning the output stream flags from audio flinger to audio policy
software output descriptor allows for improved decision making in audio
policy.

Test: lunch aosp_cf_x86_phone-next-eng # Enable HIDL audio HAL
      atest CtsMediaAudioTestCases:android.media.audio.cts.LoopbackPassthroughTest
      => verify through logging that SwAudioOutputDescriptor open flags
         returned as 0x401 (including AUDIO_OUTPUT_FLAG_IEC958_NONAUDIO)
         which is modified from the supplied 0x1 (AUDIO_OUTPUT_FLAG_DIRECT only)
      atest audiopolicy_tests
Bug: 311830316
Change-Id: I212e80779f6fee956d1c55e6c769d89260615e8c