DINNER last night at the Riviera, the Regal Hongkong's rooftop Mediterranean restaurant, where hotel PR manager Christina Koh asked: ''Is there any establishment in Hongkong with more chandeliers than us?'' At the last count the hotel had 310 Swarovski chandeliers. Singaporean Christina, who next week takes up a posting at the Peninsula Palace in Beijing, claims the record. Anyone dispute that?