qcom: Add support for custom device specific paths

* There are many supported devices with common trees,
  and they may wish to put their hals there.
* Allow setting the path to the hal by using
  DEVICE_SPECIFIC_<component>_PATH when
  USE_DEVICE_SPECIFIC_<component> is true.

Change-Id: I1335d322cd43440b028b51cff6023dd05e1d1024