Top motivator of USC football Ryan Davidson, USC's good luck charm, arrives today. STEVE BISHEFF Register columnist sbisheff@ocregister.com USC fan and cancer survivor Ryan Davidson, center, joined Reggie Bush (5) and LenDale White (21) at the Orange Bowl in January. The 12-year-old regularly corresponds with team members. PHOTOS COURTESY KIRBY DAVIDSON LOS ANGELES – A lot of the pressure and anxiety of Big Game Week will dissipate at USC today. The team's official "Good Luck Charm" is due to arrive on campus from Wisconsin. His name is Ryan Davidson, and he is a skinny, brown-haired, blue-eyed, 12-year-old boy with a...