correct wrong function name of d_put in kernel document and source comment

no function named d_put(), it should be dput().

Impact: fix document and comment, no functionality changed
Signed-off-by: Zhao Lei <zhaolei@cn.fuijtsu.com>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/vfs.txt

@@ -931,7 +931,7 @@ manipulate dentries:
   d_lookup: look up a dentry given its parent and path name component
 	It looks up the child of that given name from the dcache
 	hash table. If it is found, the reference count is incremented
-	and the dentry is returned. The caller must use d_put()
+	and the dentry is returned. The caller must use dput()
 	to free the dentry when it finishes using it.
 
 For further information on dentry locking, please refer to the document

fs/dcache.c

@@ -1332,7 +1332,7 @@ err_out:
  *
  * Searches the children of the parent dentry for the name in question. If
  * the dentry is found its reference count is incremented and the dentry
- * is returned. The caller must use d_put to free the entry when it has
+ * is returned. The caller must use dput to free the entry when it has
  * finished using it. %NULL is returned on failure.
  *
  * __d_lookup is dcache_lock free. The hash list is protected using RCU.