SiriusXM has started to pivot towards podcasting in light of Howard Stern’s rumored retirement from the popular satellite radio station. RadarOnline.com can reveal the audio platform has thrown millions of dollars into popular online shows such as Smartless and Call Her Daddy to help bring in new subscribers and rival the likes of Spotify. SiriusXM president and chief content officer Scott Greenstein has written big checks to acquire two of the biggest online podcasts, paying $100 million-plus to air their shows on the satellite radio giant. Greenstein said: “When you look at what’s going on w…