Fixed FreeBSD build

(cherry picked from commit d9e6dcc650fd96c66d1177438d1e0ee9b624c21c)

src/core/linux/SDL_evdev_kbd.c

@@ -827,6 +827,9 @@ SDL_EVDEV_keyboard_state *SDL_EVDEV_kbd_init(void)
     return NULL;
 }
 
+void SDL_EVDEV_kbd_set_muted(SDL_EVDEV_keyboard_state *state, SDL_bool muted)
+{
+}
 void SDL_EVDEV_kbd_keycode(SDL_EVDEV_keyboard_state *state, unsigned int keycode, int down)
 {
 }