hal: Changes in HAL to load the correct mixer file

Newer msm chips may support multiple codecs, leading
to existence of multiple mixer paths files once for each.
Below change implements a generic algorithm to accommodate
this change.

Get the codec internal name i.e. tomtom, tasha etc.
from the sound card name and form the mixer paths
file name dynamically. This is generic way of picking
any codec name based mixer files in future with no
code change. This code assumes mixer files are formed with
format as mixer_paths_internalcodecname.xml.
e.g. mixer_paths_tasha.xml etc.

If this dynamically read mixer files fails to open then it
falls back to default mixer file i.e. mixer_paths.xml. This is
done to preserve backward compatibility but not mandatory as
long as the mixer files are named as per above assumption.

Change-Id: Iefceaee525093e8b6a4fb06f6dd4649a262fbf12