floss: implement |cras_lea_iodev|

This CL implements |cras_lea_iodev| and completes fundamental CUJs.

BUG=b:317682584
TEST=Apply full patch series and verify unicast works

Change-Id: Iaf5b124700a03c2a07e31bf759cc21573c5870c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/5465550
Tested-by: [email protected] <[email protected]>
Reviewed-by: Hsinyu Chao <[email protected]>
Commit-Queue: Jeremy Wu <[email protected]>

Author: Jeremy Wu