Generalize custom uniform generator for floating point data types with 16 bits

- Change name of uniform_real_distribution_fp16 to uniform_real_distribution_16bit, and make it also accept bfloat16 data type

Resolves: COMPMID-4057

Signed-off-by: Giorgio Arena <giorgio.arena@arm.com>
Change-Id: Id2f1a84b9c9f09cb260a0785add4fc5954d5853a
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4768
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/tests/validation/fixtures/GEMMFixture.h b/tests/validation/fixtures/GEMMFixture.h
index 0c2f0a4..192e77e 100644
--- a/tests/validation/fixtures/GEMMFixture.h
+++ b/tests/validation/fixtures/GEMMFixture.h
@@ -64,7 +64,7 @@
         {
             case DataType::F16:
             {
-                arm_compute::utils::uniform_real_distribution_fp16 distribution{ float(lo), float(hi) };
+                arm_compute::utils::uniform_real_distribution_16bit<half> distribution{ float(lo), float(hi) };
                 library->fill(tensor, distribution, i);
                 break;
             }