Do not use BNNS copy when dtypes differ in CoreML

Author: metascroy

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

@@ -123,6 +123,9 @@ 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;
+    }
     if (dst.layout().num_bytes() < src.layout().num_bytes()) {
         return false;
     }