Combine flour, baking soda, and salt, stirring with a whisk. Place granulated sugar and butter in a large bowl, beat with a mixer at medium speed until well blended. Add eggs, 1 at a time, beating well after each addition. Add banana, yogurt, rum, and vanilla, beat until blended. Add flour mixture, beat at low speed just until moist. Stir in 1/2 cup coconut.