Rapper rose from ashes of disappointing album to top of the charts and 10 Grammy nominations.   It's fitting that Eminem is planning to return to the big screen next year in the "8 Mile"-inspired boxing film "Southpaw." Because like Rocky after he was counted down and out so many times in that famous pugilist movie serial, Marshall Mathers seemed like he'd run out of gas in 2009 only to come…