Support multiple pipes for rerouting

Support multiple pipes for rerouting

The implementation for "remote submix" supported only one pipe
  to capture the output of a mix.
This CL adds support for multiple pipes to support capturing
  multiple audio routes.
The structure for the r_submix audio device holds an array
  of route configurations (route_config), each referencing
  the input and output of the pipe dedicated to this route.
  Each route is associated to a unique address. Standby
  status is maintained per stream.

Bug 16009464

Change-Id: Ie164c4ad2a6d8138f825484e7faf29a974ccf82e