By Zach Koons The Cincinnati ballcarrier made good on his promise after scoring a Week 18 touchdown, but now faces discipline from the league. Bengals running back Joe Mixon made waves around the NFL when he broke out a coin flip celebration after scoring a touchdown in last Sunday’s regular season finale against the Ravens. So much so, that he’s received a fine from the league office. However, the Cincinnati ballcarrier doesn’t appear prepared to pay just yet. Mixon was fined $13,261 for his touchdown celebration, in which he pulled a coin out of his glove and flipped it while in the end zone…