Updating add operator with name space changes

backends/cadence/aot/functions_hifi.yaml

@@ -25,7 +25,7 @@
 - op: add.out
   kernels:
     - arg_meta: null
-      kernel_name: impl::HiFi::add_out
+      kernel_name: cadence::impl::HiFi::add_out
 
 - op: bmm.out
   kernels:

backends/cadence/hifi/operators/op_add.cpp

@@ -22,6 +22,7 @@ using executorch::runtime::CppTypeToScalarType;
 using executorch::runtime::KernelRuntimeContext;
 using torch::executor::Error;
 
+namespace cadence {
 namespace impl {
 namespace HiFi {
 namespace native {
@@ -202,3 +203,4 @@ Tensor& add_out(
 } // namespace native
 } // namespace HiFi
 } // namespace impl
+} // namespace cadence