portaudio: expose seperate indexes for input/output devices

- Portaudio enumerates all input and output devices in a single
  list, but we split them up in the selection models in lrc. This
  patch exposes device indexes based on device type, converts them
  to an Portaudio index for saving to preferences.

- This patch also catches out of range values incoming from the
  saved preferences. This can happen if we decide to switch default
  host APIs in portaudio, or if someone's cat walks on their laptop
  while they edit their config.

Change-Id: I350f283588745fe4186ae11a8410d7c9374b72ee