bcachefs: target_congested -> get_random_u32_below()

get_random_u32_below() has a better algorithm than bch2_rand_range(),
it just didn't exist at the time.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/io_read.c

@@ -59,7 +59,7 @@ static bool bch2_target_congested(struct bch_fs *c, u16 target)
 	}
 	rcu_read_unlock();
 
-	return bch2_rand_range(nr * CONGESTED_MAX) < total;
+	return get_random_u32_below(nr * CONGESTED_MAX) < total;
 }
 
 #else