consumerir: Allow devices to override default configs

* This is cleaner than hacking up makefiles
* This brings us closer to what other hals
  in this repo are doing (e.g. lights, power)
  and this is done following their example
* As a note, haggertk suggested this when we
  added the inital unified hal, but I never
  got around to doing it

Change-Id: I7c911c5afc2b67308d7135b50a4863a6a9480035
Signed-off-by: Paul Keith <javelinanddart@gmail.com>