codec2: read fallback ION params from system properties

Bug: 144995284

Test: Manually change system.prop, see if it takes effect.
In addition, check pid of the log from:

  adb logcat | grep -E 'C2Store.*Default ION'

and then verify the logs are coming from media.swcodec by:

  adb shell ps <pid>

Change-Id: Ie54fbb28ca539113e432269d4d3c94bb06e139f9