Sleeping on intensity decrease is broken, remove it.

driver-opencl.c

@@ -1509,8 +1509,6 @@ static int64_t opencl_scanhash(struct thr_info *thr, struct work *work,
 			if (gpu->gpu_us_average > dynamic_us) {
 				if (gpu->intensity > MIN_INTENSITY)
 					--gpu->intensity;
-				else
-					nmsleep(gpu->gpu_us_average - dynamic_us);
 			} else if (gpu->gpu_us_average < dynamic_us / 2) {
 				if (gpu->intensity < MAX_INTENSITY)
 					++gpu->intensity;