fixed a spelling error and use RT_NULL instead of NULL in DFS

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2215 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/dfs/src/dfs_file.c

@@ -313,7 +313,7 @@ int dfs_file_flush(struct dfs_fd *fd)
  * this function will seek the offset for specified file descriptor.
  *
  * @param fd the file descriptor.
- * @param offset the offset to be seeked.
+ * @param offset the offset to be sought.
  *
  * @return the current position after seek.
  */

components/dfs/src/dfs_fs.c

@@ -436,7 +436,7 @@ int dfs_statfs(const char *path, struct statfs *buffer)
 	struct dfs_filesystem *fs;
 
 	fs = dfs_filesystem_lookup(path);
-	if (fs != NULL)
+	if (fs != RT_NULL)
 	{
 		if (fs->ops->statfs != RT_NULL)
 			return fs->ops->statfs(fs, buffer);