IVGCVSW-7145: BatchMatMul Fix for Raspi Cross Compile Failing

  * Changed long variable declaration to int

Signed-off-by: Samuel Yap <samuel.yap@arm.com>
Change-Id: I2df6f8f6df8780e48e09f7e68c04626a8a8a207d
diff --git a/src/backends/reference/workloads/BatchMatMulImpl.cpp b/src/backends/reference/workloads/BatchMatMulImpl.cpp
index 74a358c..6693f15 100644
--- a/src/backends/reference/workloads/BatchMatMulImpl.cpp
+++ b/src/backends/reference/workloads/BatchMatMulImpl.cpp
@@ -73,7 +73,8 @@
 void BatchMatMul::AdjustAxesToMulForUnequalRanks(
     std::pair<std::pair<unsigned int, unsigned int>, std::pair<unsigned int, unsigned int>>& axesToMul)
 {
-    long rankDiff = static_cast<long>(inputXInfo.GetNumDimensions()) - inputYInfo.GetNumDimensions();
+    int rankDiff = static_cast<int>(inputXInfo.GetNumDimensions()) -
+                   static_cast<int>(inputYInfo.GetNumDimensions());
     if(rankDiff == 0)
     {
         return;