By Lisa Richwine LOS ANGELES (Reuters) – DreamWorks Animation SKG Inc could soon have a new Japanese owner in a deal that highlights the challenges facing Hollywood’s smaller studios in remaining independent and could prompt a string of other deals. Over the weekend, a source said DreamWorks, the studio best known for movie franchises including “Shrek” and “Madagascar,” was in talks about a possible sale to SoftBank Corp, the cash-rich Japanese communications and media company. …