Jim Cramer isn't holding back. On CNBC's Mad Money, he called Micron Technology Inc (NASDAQ: MU) "unstoppable" after its blockbuster fourth quarter earnings, saying the stock has more room to run and advising viewers to "buy on weakness."Track MU stock here.A Titanic Quarter, Says Cramer"Micron's revenue was up 46% year-over-year, almost 22% from the previous quarter…almost impossible to do," Cramer said, highlighting the company's stellar EPS of $3.30 versus$2.55 expected. Gross margins soared nearly 900 ...