Move 'session' field to AudioPortExtSys AIDL

The 'session' field is only used by the framework (if at all),
so it was moved from the HAL AIDL to the system-specific part.

Bug: 205884982
Test: m
Merged-In: I352552488899459055724e74545cb0f81f2e7eab
Change-Id: I352552488899459055724e74545cb0f81f2e7eab
(cherry picked from commit 186cdca36776c33a14d8ff7b0c622cc10f66e170)
2 files changed