twsi: trace register accesses only when debug level is at least two

Callers already report all interesting values or actions,
so the traces are mostly redundant.

sys/dev/iicbus/twsi/twsi.c

@@ -109,15 +109,17 @@ TWSI_READ(struct twsi_softc *sc, bus_size_t off)
 	uint32_t val;
 
 	val = bus_read_4(sc->res[0], off);
-	debugf(sc->dev, "read %x from %lx\n", val, off);
+	if (twsi_debug > 1)
+		debugf(sc->dev, "read %x from %lx\n", val, off);
 	return (val);
 }
 
 static __inline void
 TWSI_WRITE(struct twsi_softc *sc, bus_size_t off, uint32_t val)
 {
 
-	debugf(sc->dev, "Writing %x to %lx\n", val, off);
+	if (twsi_debug > 1)
+		debugf(sc->dev, "Writing %x to %lx\n", val, off);
 	bus_write_4(sc->res[0], off, val);
 }