IVGCVSW-7109: Add Batch MatMul front end support - Reference

  * Descriptors added for BatchMatMul
  * Layer definition added
  * Input validation added (will likely change when opt. param support comes in)
  * Ref workload implementation for BatchMatMul added (will also change with opt. param support)
  * Ref layer tests made for BatchMatMul
  * CMake and other build files updated

Signed-off-by: Samuel Yap <samuel.yap@arm.com>
Change-Id: Ic885301da543ee0fbe7922b85e7f9658c4efc617
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index d9a5a1d..ed942e6 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -23,6 +23,7 @@
         RefTensorHandleFactory.cpp \
         workloads/Activation.cpp \
         workloads/ArgMinMax.cpp \
+        workloads/BatchMatMulImpl.cpp \
         workloads/BatchNormImpl.cpp \
         workloads/BatchToSpaceNd.cpp \
         workloads/Broadcast.cpp \
@@ -49,6 +50,7 @@
         workloads/Reduce.cpp \
         workloads/RefActivationWorkload.cpp \
         workloads/RefArgMinMaxWorkload.cpp \
+        workloads/RefBatchMatMulWorkload.cpp \
         workloads/RefBatchNormalizationWorkload.cpp \
         workloads/RefBatchToSpaceNdWorkload.cpp \
         workloads/RefCastWorkload.cpp \