If you have to ask if something is racist/sexist/offensive in any way, you should probably just assume it is.
"Jimmies" -- a New England/Eastern US colloquialism referring to chocolate sprinkles, or sprinkles in general -- has joined the pantheon of cringe-worthy antiquated phrases you might hear your grandma drop in Friendly's while you cower behind a lamented specials board. Frankly, there's a constituency that thinks the term is straight-up racist, a slur directed towards African-Americans.
Obviously, if the intent is there, it doesn't matter if other people think it's offensive or not. But are the origins of the term truly dubious, or has its meaning been warped by time?