Deprecated BF16 support in DepthConvert

* Removed BF16 validation tests for DepthConvert

* Revert back to using inline assembly to convert to/from BF16

* Resolves COMPMID-5800

Change-Id: I803b2ad19ead297417f780c97c5b724cca6b394c
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/8929
Reviewed-by: Jakub Sujak <jakub.sujak@arm.com>
Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/filedefs.json b/filedefs.json
index c8a66e3..3422eeb 100644
--- a/filedefs.json
+++ b/filedefs.json
@@ -5,7 +5,7 @@
                 "cxxflags": ["-march=armv8.2-a"]
             },
             "armv8.2-a": {
-                "cxxflags": ["-march=armv8.2-a+fp16+bf16"],
+                "cxxflags": ["-march=armv8.2-a+fp16"],
                 "cppdefines": ["ARM_COMPUTE_ENABLE_FP16"]
             },
             "armv8.2-a-sve": {