He's wrecked hotel rooms. He dates a model. Ergo, Johnny Depp must be a rock star. To that end he, along with Butthole Surfer Gibby Haynes, has given us P, his not-so-long-awaited musical debut, most notable for its strained bid for attention (a deadpan makeover of ABBA's ''Dancing Queen'') and credibility (with would-be eclectic forays into rockabilly, blues, and dub reggae). Lucky us.