One of two Wall Street analysts that had a sell rating on Apple stock threw in the towel. The other still thinks that AAPL shares could drop 40%. Is the sizable downside risk realistic?On the first day of September, one of the rare Wall Street bears on Apple stock finally gave in and dropped his sell rating. The last remaining one still sees shares dropping to a price target of $90, representing risk of loss of around 40%.Could New Street’s Pierre Ferragu, the last remaining Apple bear on Wall