Enable BNNS copy for FP16 to FP32

Differential Revision: D80465059

Pull Request resolved: #13477

Author: metascroy

backends/apple/coreml/runtime/delegate/multiarray.mm

@@ -124,7 +124,10 @@ bool init_bnns_descriptor(BNNSNDArrayDescriptor& bnns_descriptor, const MultiArr
 
 bool copy_using_bnns(const MultiArray& src, MultiArray& dst) {
     if (src.layout().dataType() != dst.layout().dataType()) {
-        return false;
+        // Copying from FP16 to FP32 is supported and this is a common use case
+        if (!(src.layout().dataType() == MultiArray::DataType::Float16 && dst.layout().dataType() == MultiArray::DataType::Float32)) {
+            return false;
+        }
     }
     if (dst.layout().num_bytes() < src.layout().num_bytes()) {
         return false;