mm: compaction: Update try_to_compact_pages()kerneldoc comment

Parameters were added without documentation, tut tut.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -926,6 +926,8 @@ int sysctl_extfrag_threshold = 500;
  * @gfp_mask: The GFP mask of the current allocation
  * @nodemask: The allowed nodes to allocate from
  * @sync: Whether migration is synchronous or not
+ * @contended: Return value that is true if compaction was aborted due to lock contention
+ * @page: Optionally capture a free page of the requested order during compaction
  *
  * This is the main entry point for direct page compaction.
  */