joystick: Fix redetection of HIDAPI joysticks after reinitializing

The HIDAPI joystick driver doesn't properly reset the change counter
it uses to track if re-enumeration is needed when the joystick
subsystem is quit and then reinitialized.

The first SDL_Init(SDL_INIT_JOYSTICK) will result in the expected
HIDAPI joysticks appearing, but subsequent calls will result in no
joysticks being enumerated until another HIDAPI joystick is added
or removed from the system.

src/joystick/hidapi/SDL_hidapijoystick.c

@@ -1076,6 +1076,7 @@ HIDAPI_JoystickQuit(void)
 
     SDL_hid_exit();
 
+    SDL_HIDAPI_change_count = 0;
     shutting_down = SDL_FALSE;
     initialized = SDL_FALSE;
 }