A subway rider was knifed in the gut on a Queens train Saturday morning after asking another passenger to stop talking loudly on his cell phone, cops said. The 54-year-old victim made the request of the stranger while riding an E train at the Jamaica Center/Parsons Ave. station around 11 a.m., police said.  The chatty subway rider allegedly responded by punching the victim several times in the face before stabbing him in the abdomen, according to police.  The attacker jumped off the train at