hwrng: don't double-check old_rng.

Interesting anti-pattern.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/core.c

@@ -472,14 +472,13 @@ int hwrng_register(struct hwrng *rng)
 	}
 
 	old_rng = current_rng;
+	err = 0;
 	if (!old_rng) {
 		err = hwrng_init(rng);
 		if (err)
 			goto out_unlock;
 		set_current_rng(rng);
-	}
-	err = 0;
-	if (!old_rng) {
+
 		err = register_miscdev();
 		if (err) {
 			drop_current_rng();