POP/ROCK U2: War. (Island Records: 90067-1.) This refreshing new album from U2 comes at an important time in the music industry. It reconfirms that hard-driving rock music can have lyrics which are fresh and stimulating - not just redundant words of love and trite bromides. ''War'' is undoubtebly one of the most powerful rock albums of 1983. The theme of the album is best seen in songs such as ''Sunday Bloody Sunday'' and ''New Year's Day,'' both of which paint a clear-etched portrait of strife-torn Northern Ireland. As a band from the Republic of Ireland , they can give the issues involved in this battle-ravaged region a close perspective. There are echoes of hope in their lyrics - but the hope is full of desperation and questions, asking why such battle is necessary, as in ''Sunday Bloody Sunday'': ''And the battle's just begun, there's many lost, but tell me who has won? The four young musicians that are U2 play and sing with a fervor as intense as the album's subject matter, and every cut has a compelling beat.