Heartwarming, life-affirming cinema always has the perilous potential for turning mawkish. But uplifting music, free of the sometimes overwrought dimensions of moviemaking, is usually free of such burdens. Zeroing in on the advantages of the latter and mostly avoiding the pitfalls of the former, filmmaker Gurinder Chadha succeeds in achieving that exuberant, ineffable feeling when music can change your life. In her inspiring new drama “Blinded by the Light,” Chadha (“Bend it Like Beckham“) taps into the anthemic spirit of the always-stirring songs of Bruce Springsteen.