Documentation: dmanegine: move dmatest.txt to dmaengine folder

Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/Documentation/dmatest.txt b/Documentation/dmaengine/dmatest.txt
similarity index 100%
rename from Documentation/dmatest.txt
rename to Documentation/dmaengine/dmatest.txt