hal: msm8939: use mixer paths mtp xml for 8939 mtp

The mtp 8939 hardware has a bug due to which the primary
mic is the top mic.
The change chooses the right mixer paths which takes care
of swapping the mics which uses the bottom mic for
primary mic.

Change-Id: I370268e98178acc8a41bc733d2df83def227c1fc