Introduce macros to build IDs from controller and channel number, and to
extract them. Modify the edma_alloc_slot function to take an extra argument
for the controller.

Also update ASoC drivers to use API.  ASoC changes
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Reviewed-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>