By Martin Baccardax Softbank will retain a pre-paid $1.25 billion breakup fee after the collapse of its planned $40 sale of chip designer Arm Holdings to Nvidia. Nvidia (NVDA) – Get NVIDIA Corporation Report shares slipped lower Tuesday after it formally called-off its planned $40 billion takeover of chipmaker Arm Holdings from Japan’s SoftBank Group. Softbank, which purchased Arm for around $32 billion in 2016, is now looking to list the chip designing business following a series of push-backs on the sale to Nvidia from regulators on both sides of the Atlantic, as well as in China, over the i…