By Sean Penn for Rollingstone Magazine   He sits in a turquoise-and-navy paisley long-sleeve button-down shirt and clean black slacks on a randomly placed stool. The signature mustache that he wore in our last meeting, now gone. His trademark black trucker’s hat, absent. His hair combed, or perhaps cap-matted, conjuring the vision of a wide-eyed schoolboy unsure of his teacher’s summons. …