LeAudio: Prepare data path before "receiver start ready"

We should have the data path prepared before we send the
ReceiverStartRedy ASCS operation.

Also this patch removes not necessary code for handling
autonomous QoS Configured -> Streaming state transition.
It is removed, as this is impossible to happen with Android
stack, because Android create CISes only when all ASEs gets
into Enabling state.

Bug: 227116068
Test: atest --host bluetooth_le_audio_test bluetooth_le_audio_client_test
Change-Id: Ic33e2b9207ed3ac6302e3d04a360b2fac1dcd9c7