Bank of America Merrill Lynch has done an about-face on RadioShack­ Corp.’s stock, making its “underperform” rating a “buy” and raising the price target 25 percent to $2.50. In past weeks, Dow Jones reports, the company booted its CEO and lost its spot on the S&P MidCap 400, but its market value is just 20 percent of inventory value and it has $1 billion of liquidity.