LeAudio: Adjust stream configurations

This change makes sure that when switching from Single
to Dual device configuration we won't change the frame
duration (eg. from 7.5 to 10ms) as there is no way to
reconfigure AF without closing the audio session, and
doing so would break the seamless experience.

Bug: 271941416
Tag: #feature
Test: atest --host bluetooth_le_audio_test --no-bazel-mode
Change-Id: I37908b9f18be470a52de9e560ba314425c9668c7