Smooth out Sienna tuning (#1292)

Current Sienna tuning leads to pretty significant bouncing and oversteering, this change fixes it. Thanks to @Jax for finding some great values and checking with a Toyota mechanic on the real steer ratio for Siennas!
old-commit-hash: e0ba222336

selfdrive/car/toyota/interface.py

@@ -195,10 +195,10 @@ class CarInterface(CarInterfaceBase):
       stop_and_go = True
       ret.safetyParam = 73
       ret.wheelbase = 3.03
-      ret.steerRatio = 16.0
+      ret.steerRatio = 15.5
       tire_stiffness_factor = 0.444
       ret.mass = 4590. * CV.LB_TO_KG + STD_CARGO_KG
-      ret.lateralTuning.pid.kpV, ret.lateralTuning.pid.kiV = [[0.3], [0.05]]
+      ret.lateralTuning.pid.kpV, ret.lateralTuning.pid.kiV = [[0.19], [0.02]]
       ret.lateralTuning.pid.kf = 0.00007818594
 
     elif candidate == CAR.LEXUS_IS: