dt-bindings: soc: add bindings for Intel HPS Copy Engine

commit aa1a83f84f199623e2926e6ca876402d40fde191 from
https://github.com/altera-opensource/linux-socfpga.git



[upstream commit 79af73b3]

Add device tree bindings documentation for the Intel Hard
Processor System (HPS) Copy Engine.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>