hal: Add support for multiple hardware variants

- Most of the targets supports multiple hardware variants such as
  MTP, CDP, Fluid, Liquid etc. The mixer paths for certain devices
  may vary on some of the variants. For example, the mixer controls
  for speaker device are different on msm8974 MTP and Fluid variants.
- Update audio HAL to select corresponding entry in the
  mixer_paths.xml file based on HW information.

Change-Id: I060f2e6c331344dd41417c19fb688ff27a129308

Conflicts:

	hal/Android.mk