align the cluster size restriction wordings

Author: bashbaug

OpenCL_C.txt

@@ -14959,9 +14959,9 @@ gentype sub_group_clustered_rotate(
     The value of _delta_ is required to be dynamically-uniform for all work
     items in the sub-group, otherwise the behavior is undefined.
 
-    _clustersize_ must be an integer constant expression and a power of two,
-    smaller than or equal to the maximum sub-group size, otherwise the
-    behavior is undefined.
+    Behavior is undefined if _clustersize_ is not an integer constant
+    expression, is not a power-of-two, or is greater than the maximum size of a
+    sub-group within the dispatch.
 
     The return value is undefined if the work item with sub-group local ID
     equal to the calculated index is inactive.