dsp: afe: Enhance and expose API for configuring ext clk

To configure the external clock, the client (machine driver) is expected
to configure the clock attributes (M, N, D, div2x, clk root, etc.) and if
required, to toggle the external clock source in the registered callback
function, before sending the param to the DSP. Expose the API to the
clock driver for the same. During clock disable, the sequence of
operations is reversed.

Change-Id: I289625e40c3a9c102270eae3c10ad7bf1a112f4f
Signed-off-by: Abhilash Sathyanarayana <quic_abhisath@quicinc.com>