Fixed build warning

src/joystick/hidapi/SDL_hidapi_steam.c

@@ -1034,6 +1034,12 @@ HIDAPI_DriverSteam_RumbleJoystick(SDL_HIDAPI_Device *device, SDL_Joystick *joyst
     return SDL_Unsupported();
 }
 
+static int
+HIDAPI_DriverSteam_RumbleJoystickTriggers(SDL_HIDAPI_Device *device, SDL_Joystick *joystick, Uint16 left_rumble, Uint16 right_rumble)
+{
+    return SDL_Unsupported();
+}
+
 static SDL_bool
 HIDAPI_DriverSteam_HasJoystickLED(SDL_HIDAPI_Device *device, SDL_Joystick *joystick)
 {
@@ -1182,6 +1188,7 @@ SDL_HIDAPI_DeviceDriver SDL_HIDAPI_DriverSteam =
     HIDAPI_DriverSteam_UpdateDevice,
     HIDAPI_DriverSteam_OpenJoystick,
     HIDAPI_DriverSteam_RumbleJoystick,
+    HIDAPI_DriverSteam_RumbleJoystickTriggers,
     HIDAPI_DriverSteam_HasJoystickLED,
     HIDAPI_DriverSteam_SetJoystickLED,
     HIDAPI_DriverSteam_CloseJoystick,