What do you think of this idea? Should restaurants start doing this? Or - are you tied to your cell phone that you can't part with it for just a bit? By Martha C. White  Hold that call: At Eva, a New American restaurant in Los Angeles, diners who give up their cell phones for the duration of the meal get a 5 percent discount.  “When I first heard about it, I loved it,” said Jaime Oikle, founder…