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, modify the MMC and ASoC drivers to reflect the above changes.
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>