dsp: afe: add interface to update dp audio stream index

For DP audio Multi Stream Transport, add an interface
to set DP controller and DP stream index for display
port audio AFE port.

Change-Id: I6efbb6937a7849e5840a93541961414eb9049863
Signed-off-by: Karthikeyan Mani <kmani@codeaurora.org>