uavcan: increase ESC max rate 200->400 Hz

- this should run synchronized with the rate controller and can be
limited by IMU_GYRO_RATEMAX

src/drivers/uavcan/actuators/esc.hpp

@@ -58,7 +58,7 @@ class UavcanEscController
 {
 public:
 	static constexpr int MAX_ACTUATORS = esc_status_s::CONNECTED_ESC_MAX;
-	static constexpr unsigned MAX_RATE_HZ = 200;			///< XXX make this configurable
+	static constexpr unsigned MAX_RATE_HZ = 400;
 	static constexpr uint16_t DISARMED_OUTPUT_VALUE = UINT16_MAX;
 
 	static_assert(uavcan::equipment::esc::RawCommand::FieldTypes::cmd::MaxSize >= MAX_ACTUATORS, "Too many actuators");