Of course the Grinch had to show up somewhere in the world of entertainment on Christmas Day. This year it was in Portugal, where all 700 of the country's new--and thriving--pirate radio stations were forced off the air Sunday by official decree. The government, determined to end the airwave chaos that has developed in recent years, announced three months ago that all illegal stations must stop transmitting by midnight on Christmas Eve. The ban will remain until a government commission rules on what operators will be given the legal franchises for 400 local FM stations around the country. The hearings could last as long as six months.