a2dp: Fix value of CODEC_ID_AAC

Incorrectly set to 0x1 instead of 0x2.
The value is normative (defined by A2DP specification).

Bug: 305734815
Bug: 308686081
Test: m com.android.btservice
Change-Id: I8709577442ab07e8e0f64933c55c99844bcda3a3