By Ross Kerber, Echo Wang and Joey Roulette BOSTON/NEW YORK, Dec 11 (Reuters) - Investors welcomed reports that SpaceX (SPAX.PVT) was mulling a potential IPO that would help fund Elon Musk's Mars ambitions and value the rocket and satellite company at more than $1 trillion, as some have been waiting for years to buy into the company. SpaceX is looking to raise ​more than$25 billion in an initial public offering that could come as early as June, a person familiar with the matter told Reuters. Though it ...