Each left/right pair of AIF input/output channels can be swapped or
combined. This is useful for sending a mono audio source to both sides
of a stereo sink, or for creating complex mixing scenarios.

Add the support to control this feature from userspace.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20201001021148.15852-8-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>