Updated dpnp.mean() per review comment

Author: antonwolfy

dpnp/dpnp_iface_statistics.py

@@ -614,13 +614,12 @@ def mean(a, /, axis=None, dtype=None, out=None, keepdims=False, *, where=True):
 
     dpnp.check_limitations(where=where)
 
-    dpt_array = dpnp.get_usm_ndarray(a)
-    result = dpnp_array._create_from_usm_ndarray(
-        dpt.mean(dpt_array, axis=axis, keepdims=keepdims)
-    )
-    result = result.astype(dtype) if dtype is not None else result
+    usm_a = dpnp.get_usm_ndarray(a)
+    usm_res = dpt.mean(usm_a, axis=axis, keepdims=keepdims)
+    if dtype is not None:
+        usm_res = dpt.astype(usm_res, dtype)
 
-    return dpnp.get_result_array(result, out, casting="same_kind")
+    return dpnp.get_result_array(usm_res, out, casting="same_kind")
 
 
 def median(x1, axis=None, out=None, overwrite_input=False, keepdims=False):