hwrng: core - allow perfect entropy from hardware devices

Hardware random number quality is measured from 0 (no entropy) to 1024
(perfect entropy). Allow hardware devices to assert the full range by
truncating the device-provided value at 1024 instead of 1023.
Signed-off-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/core.c

@@ -179,7 +179,8 @@ static int hwrng_init(struct hwrng *rng)
 	add_early_randomness(rng);
 
 	current_quality = rng->quality ? : default_quality;
-	current_quality &= 1023;
+	if (current_quality > 1024)
+		current_quality = 1024;
 
 	if (current_quality == 0 && hwrng_fill)
 		kthread_stop(hwrng_fill);