Purdue freshman guard Braden Smith scored 20 points on 6-of-8 shooting and made three 3-pointers in a victory over Marquette. The team improved to 3-0 for the second consecutive season before a trip to Portland, Ore., for the Phil Knight Legacy Tournament. WEST LAFAYETTE, Ind. — Purdue basketball, facing its toughest challenge so far this season, was lifted by freshman guard Braden Smith’s second-half scoring efforts in a 75-70 victory against Marquette on Tuesday night in Mackey Arena. Smith scored 15 of his team-high 20 points after halftime, matching junior center Zach Edey’s scoring output for the Boilermakers, who trailed…