[CPU][Bugfix] Fix ppc64le CPU build (#30871)

Signed-off-by: Nishidha Panpaliya <nishidha.panpaliya@partner.ibm.com>

csrc/cpu/utils.hpp

@@ -37,10 +37,12 @@ struct VecTypeTrait<c10::BFloat16> {
 };
 #endif
 
+#if !defined(__powerpc__)
 template <>
 struct VecTypeTrait<c10::Half> {
   using vec_t = vec_op::FP16Vec16;
 };
+#endif
 
 struct Counter {
   std::atomic<int64_t> counter;