Add dummy symlinks to actual implementation

* Include paths expect headers to be at
  hardware/qcom/audio-caf/$(TARGET_BOARD_PLATFORM), so create symlinks to
  the 8974 implementation at hardware/qcom/audio-caf/msm8974.
* (cdesai): Symlink the Android.mk too, so that the build
  system can pick that up and build what's in here.

Change-Id: Ic089ef7f8d635db4de2f8d238f6d2c4e96d05799
Signed-off-by: Chirayu Desai <chirayudesai1@gmail.com>