Fix compile error in prelu_op.

paddle/operators/prelu_op.h

@@ -54,8 +54,8 @@ class PReluKernel : public framework::OpKernel {
 
     int numel = x->numel();
 
-    auto place = context.GetPlace();
-    Transform(place, x_ptr, x_ptr + numel, o_ptr, PReluFunctor<T>(alpha_ptr));
+    Transform(context.device_context(), x_ptr, x_ptr + numel, o_ptr,
+              PReluFunctor<T>(alpha_ptr));
   }
 };
 
@@ -91,9 +91,8 @@ class PReluGradKernel : public framework::OpKernel {
     const T* out_ptr = out->data<T>();
     int numel = dx->numel();
 
-    auto place = context.GetPlace();
-    Transform(place, out_ptr, out_ptr + numel, dout_ptr, dx_ptr,
-              PReluGradFunctor<T>(alpha_ptr));
+    Transform(context.device_context(), out_ptr, out_ptr + numel, dout_ptr,
+              dx_ptr, PReluGradFunctor<T>(alpha_ptr));
 
     // TODO (Zhuoyuan): add dalpha upgrade when GPU kernels ready
   }