ASoC: Add DTMF support for Audio usecase

Add  support to route DTMF source AFE port 
to any other RX port. this support is already 
present  during voice call. This change adds t
same support during audio usecase.

Change-Id: I78fa1049e04de6d7af535929beac209f4c8bc1c6
Signed-off-by: Jhansi Konathala <cjkonat@codeaurora.org>