Grammy stars free to sing out on war By GEORGE RUSH and ISAAC GUZMAN DAILY NEWS STAFF WRITERS Get ready for antiwar protests at tomorrow night's Grammy Awards ceremony. Despite a report that CBS executives had considered blocking politically outspoken rockers, the network said last night it would not pull the plug on anyone protesting a war against Iraq. The Drudge Report, an Internet news site, quoted an anonymous CBS chieftain as saying the network would cut the microphone of any rocker who engaged in antiwar rhetoric. But CBS quickly moved to squelch the story. "There will be no restrictions...