!10463 SequenceMask doc fix and input check

From: @peilin-wang
Reviewed-by: @liangchenghui,@wuxuejian
Signed-off-by: @liangchenghui

mindspore/core/abstract/prim_arrays.cc

@@ -886,6 +886,10 @@ AbstractBasePtr InferImplSequenceMask(const AnalysisEnginePtr &, const Primitive
     maxlen_value = *static_cast<int64_t *>(maxlen_tensor->data_c());
   }
 
+  if (maxlen_value <= 0) {
+    MS_LOG(EXCEPTION) << "maxlen must be positive, but got: " << maxlen_value;
+  }
+
   ShapeVector lengths_shape = lengths->shape()->shape();
   ShapeVector lengths_shape_min = lengths->shape()->min_shape();
   if (lengths_shape_min.empty()) {

mindspore/ops/composite/array_ops.py

@@ -114,7 +114,7 @@ def sequence_mask(lengths, maxlen):
 
     Args:
         length (Tensor): Tensor to calculate the mask for. All values in this tensor must be
-          less than `maxlen`. Must be type int32 or int64.
+          less than or equal to `maxlen`. Must be type int32 or int64.
 
         maxlen (int): size of the last dimension of returned tensor. Must be positive and same
           type as elements in `lengths`.