samples: Bluetooth: Fix compatibility with Google Pixel unicast audio

Update BAP unicast server samples to work with Google Pixel:

Fix sink/source location count to match actual sink/source count,
  preventing "Codec channel setup fail" errors on phone

Increase ATT prepare count from 1 to 2 to handle phone sending
Codec Config for 3 ASEs simultaneously, avoiding Codec Config
failures during recording

Signed-off-by: Chang An <chang.an_1@nxp.com>