Use 1u literal for flags/masks calculation

Changes `1 <<` and `1<<` to use `1u`.

include/SDL3/SDL_joystick.h

@@ -429,9 +429,9 @@ typedef struct SDL_VirtualJoystickDesc
     Uint16 product_id;  /**< the USB product ID of this joystick */
     Uint16 padding;     /**< unused */
     Uint32 button_mask; /**< A mask of which buttons are valid for this controller
-                             e.g. (1 << SDL_GAMEPAD_BUTTON_SOUTH) */
+                             e.g. (1u << SDL_GAMEPAD_BUTTON_SOUTH) */
     Uint32 axis_mask;   /**< A mask of which axes are valid for this controller
-                             e.g. (1 << SDL_GAMEPAD_AXIS_LEFTX) */
+                             e.g. (1u << SDL_GAMEPAD_AXIS_LEFTX) */
     const char *name;   /**< the name of the joystick */
 
     void *userdata;     /**< User data pointer passed to callbacks */