Bluetooth: Remove credit check from Loopback tests

The Bluetooth specification doesn't require data credits
to come back within a specific timeframe, so the VTS test
can not require it.

Bug: 65269854
Test: VtsHalBlueoothV1_0TargetTest with simulated chip (no credits)
Change-Id: If2fc052d3b5236f6a3097f3d5403882226561404