btm_sco_hfp_hal_linux: Fix codec info for legacy devices

Some legacy devices don't even support HCI command Read Local Supported
Codecs, while https://r.android.com/2919865 actually relies on this
command to set up the correct codec info. This patch sets up TRANSPARENT
and CVSD without this command (follow original kernel behavior) and also
remove an unused structure.

Bug: 327547486
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: bluetooth_AdapterAUHealth.au_hfp_wbs_dut_as_sink_test.floss
      on Zork/Ezkinil (RTL8822C)
Flag: EXEMPT, Floss-only changes

Change-Id: I7c0becd09f37968464a59d891ab18c3b40efeb08