do_invalidatepage() comment typo fix

Fix a typo in the comment for do_invalidatepage().
Signed-off-by: NFengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: NAdrian Bunk <bunk@kernel.org>

mm/truncate.c

@@ -21,7 +21,7 @@
 
 
 /**
- * do_invalidatepage - invalidate part of all of a page
+ * do_invalidatepage - invalidate part or all of a page
  * @page: the page which is affected
  * @offset: the index of the truncation point
  *