ASoC: Tegra+ALC5632 machine: Add device tree binding documentation

Document device tree binding for the tegra board with ALC5632 codec
according to datasheet functional block description.

Signed-off-by: Leon Romanovsky <leon@leon.nu>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>