IVGCVSW-2371 Add Rsqrt Ref implementation

*Added Unit Tests

Change-Id: I6cceb8e6dcda35ce08415f8e5ca86019a64d26e3
diff --git a/Android.mk b/Android.mk
index 4c8c492..c02dc39 100644
--- a/Android.mk
+++ b/Android.mk
@@ -113,13 +113,14 @@
         src/armnn/layers/PermuteLayer.cpp \
         src/armnn/layers/Pooling2dLayer.cpp \
         src/armnn/layers/DivisionLayer.cpp \
-        src/armnn/layers/SubtractionLayer.cpp \
         src/armnn/layers/ReshapeLayer.cpp \
-        src/armnn/layers/SpaceToBatchNdLayer.cpp \
         src/armnn/layers/ResizeBilinearLayer.cpp \
+        src/armnn/layers/RsqrtLayer.cpp \
+        src/armnn/layers/SpaceToBatchNdLayer.cpp \
         src/armnn/layers/SoftmaxLayer.cpp \
         src/armnn/layers/SplitterLayer.cpp \
         src/armnn/layers/StridedSliceLayer.cpp \
+        src/armnn/layers/SubtractionLayer.cpp \
         src/armnn/Descriptors.cpp \
         src/armnn/Exceptions.cpp \
         src/armnn/Graph.cpp \