f2fs: remove else in f2fs_write_cache_pages()

As Christoph Hellwig point out:

	Please avoid the else by doing the goto in the branch.
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -3123,12 +3123,9 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
 			}
 
 			if (folio_test_writeback(folio)) {
-				if (wbc->sync_mode != WB_SYNC_NONE)
-					f2fs_wait_on_page_writeback(
-							&folio->page,
-							DATA, true, true);
-				else
+				if (wbc->sync_mode == WB_SYNC_NONE)
 					goto continue_unlock;
+				f2fs_wait_on_page_writeback(&folio->page, DATA, true, true);
 			}
 
 			if (!folio_clear_dirty_for_io(folio))