It’s the same song.The same line.And it’s a big hit.Green’s comeback hit, “Highball,” hit No. 1 on the Billboard Hot 100 in October.Now, the pop star has the green drink of success to thank for it.Green’s new song, “Piggybank,” was the best-selling single of 2016.The song has already sold more than 7 million copies.“Pigsybank” is …