Add cuda dependencies for benchmark

Note that nd4j is downgraded to 0.8.0 due to https://github.com/deeplearning4j/nd4j/issues/2767

Author: Atry

benchmarks/build.sbt

@@ -1,8 +1,10 @@
 enablePlugins(JmhPlugin)
 
-libraryDependencies += "org.nd4j" % "nd4j-api" % "0.9.1"
+libraryDependencies += "org.nd4j" % "nd4j-api" % "0.8.0"
 
-libraryDependencies += "org.nd4j" % "nd4j-native-platform" % "0.9.1"
+libraryDependencies += "org.nd4j" % "nd4j-cuda-8.0-platform" % "0.8.0"
+
+libraryDependencies += "org.nd4j" % "nd4j-native-platform" % "0.8.0"
 
 libraryDependencies += ("org.lwjgl" % "lwjgl" % "3.1.6").jar().classifier {
   import scala.util.Properties._