Add support for targets which have more than one ADM present. In the
interest of maintaining the same api as before, map each ADM's channels
sequentially, so adm0 would have channels 0-15, adm1 would have channels
16-31, etc.
Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org> Signed-off-by: David Brown <davidb@codeaurora.org>