aaudio: turn off RAW flag for sessions

Improve support for AudioEffects in LOW_LATENCY mode.

If a Session is requested then it is likely that effects will
be used so do not set the RAW flag. RAW flag could interfere with
creating effects on some devices.

Bug: 80203192
Test: Native Oboe Tester
Change-Id: I9e7ac8689de71b376b750259da36d5879fe4898d