Can now indicate the desired number of notifications (sub-buffers)

per fast track buffer when using the default buffer size.

There is no change for normal tracks, or fast tracks with a non-default buffer size.

Also fix related bugs:
Notification period was not set correctly when fast multiplier is not 1.
Incorrect warning when client adjusted notification frames.

Bug: 27819623
Bug: 28117362
Change-Id: Ifc2121e874f51718cd56ec04e4bd5f89f4963132