add ndim property to internal descriptor (#739)

Author: shssf

dpnp/dpnp_utils/dpnp_algo_utils.pyx

@@ -475,6 +475,12 @@ cdef class dpnp_descriptor:
             return self.descriptor["shape"]
         return None
 
+    @property
+    def ndim(self):
+        if self.is_valid:
+            return len(self.shape)
+        return 0
+
     @property
     def size(self):
         if self.is_valid: