leaudio: Fix channel count provided to Java layer.

This channel count is a codec configuration parameter and not a number
of channels which will be sent to remote devices.

Bug: 331775328
Test: atest bluetooth_le_audio_client_test
Flags: Exempt, trivial fix, value not yet used
Change-Id: I5e283bffaf456c71d509dde7288b8351a83d9627