Warren Buffett's Berkshire Hathaway has cut its stake in 'Call of Duty' maker Activision Blizzard amid regulatory scrutiny of its deal with Microsoft. Berkshire sold 7.4 million shares, or 12% of its position, in Activision in the fourth quarter, regulatory filings showed. Berkshire also raised its stake in Apple to 5.8% by buying 20.8 million shares.