Edit a comment to reflect an actual enum type name

There is nothing named enum_vehicle_ap_power_state_shutdown_param_type
in the Vehicle HAL source tree. The right greppable type name is
VehicleApPowerStateShutdownParam.

Test: git diff
Change-Id: Ib6c8be491df9aa6cb3143b28a12b70bd4b8c29cc
diff --git a/automotive/vehicle/2.0/types.hal b/automotive/vehicle/2.0/types.hal
index 9dfd558..1355d9f 100644
--- a/automotive/vehicle/2.0/types.hal
+++ b/automotive/vehicle/2.0/types.hal
@@ -2537,7 +2537,7 @@
      * power controller must change power state to this state to shutdown
      * system.
      *
-     * int32Values[1] : one of enum_vehicle_ap_power_state_shutdown_param_type
+     * int32Values[1] : one of VehicleApPowerStateShutdownParam
      *
      * SHUTDOWN_PRPARE may be requested from either WAIT_FOR_VHAL or ON states.
      */