btrfs: remove trivial goto label in __extent_writepage()

Since 40f765805f08 ("Btrfs: split up __extent_writepage to lower stack
usage"), done_unlocked is simply a return 0. Get rid of it.
Mid-statement block returns don seem to make the code less readable here.

Reviewed-by: Johannes Thumshirn <[e-mail]>
Signed-off-by: Omar Sandoval <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/extent_io.c

···
 	if (!epd->extent_locked) {
 		ret = writepage_delalloc(inode, page, wbc, start, &nr_written);
 		if (ret == 1)
-			goto done_unlocked;
+			return 0;
 		if (ret)
 			goto done;
 	}
···
 	ret = __extent_writepage_io(inode, page, wbc, epd,
 				    i_size, nr_written, &nr);
 	if (ret == 1)
-		goto done_unlocked;
+		return 0;
 
 done:
 	if (nr == 0) {
···
 	unlock_page(page);
 	ASSERT(ret <= 0);
 	return ret;
-
-done_unlocked:
-	return 0;
 }
 
 void wait_on_extent_buffer_writeback(struct extent_buffer *eb)