Simon Cowell is already back on his feet just days after undergoing surgery on his broken back, according to his fellow America’s Got Talent judge Heidi Klum.Over the weekend, it was reported that the 60-year-old TV mogul had been rushed to hospital with a broken back, after falling from an electric bike he was riding at his home in California.Having now undergone surgery on his back, reports have suggested that Simon has already been up walking, which his AGT co-star Heidi Klum appears to have