fix amax/amin/max/min write overflow (#47570)

paddle/phi/kernels/funcs/reduce_functor.h

@@ -177,7 +177,8 @@ struct MaxOrMinGradFunctor {
     auto zeros = dx->constant(0);
     // If there are multiple minimum or maximum elements, the subgradient of
     // each is the set [0, 1], and we pass gradient to all of them here.
-    dx->device(place) = dy->broadcast(dim) * equals.select(ones, zeros);
+    dx->device(place) = dy->broadcast(dim).reshape(x->dimensions()) *
+                        equals.select(ones, zeros);
   }
 };
 
@@ -259,7 +260,8 @@ struct AMaxOrAMinGradFunctor {
       auto equal_number = mask.sum()
                               .reshape(Eigen::array<int, 1>({1}))
                               .broadcast(Eigen::array<int, 1>({size}));
-      dx->device(place) = dy->broadcast(dim) * mask / equal_number;
+      dx->device(place) =
+          dy->broadcast(dim).reshape(x->dimensions()) * mask / equal_number;
       return;
     }