IVGCVSW-4449 Add QLstm ref implementation

* Adds ref implemenation for new HAL 1.3
  operator, QLstm.
* Adds Layer and CreateWorkload unit tests.
* Adds WorkloadData validate for QLstm.

Signed-off-by: James Conroy <james.conroy@arm.com>
Change-Id: I8a721f07ff06105e6495a1a0561b9503aa8146dc
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index 239863f..8d7f63d 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -75,6 +75,7 @@
         workloads/RefPermuteWorkload.cpp \
         workloads/RefPooling2dWorkload.cpp \
         workloads/RefPreluWorkload.cpp \
+        workloads/RefQLstmWorkload.cpp \
         workloads/RefQuantizeWorkload.cpp \
         workloads/RefReshapeWorkload.cpp \
         workloads/RefResizeBilinearWorkload.cpp \