SDL_x11dyn.h: include XInput2.h also for Xfixes

Fixes https://github.com/libsdl-org/SDL/issues/7343

src/video/x11/SDL_x11dyn.h

@@ -52,7 +52,7 @@
 #if SDL_VIDEO_DRIVER_X11_XDBE
 #include <X11/extensions/Xdbe.h>
 #endif
-#if SDL_VIDEO_DRIVER_X11_XINPUT2
+#if SDL_VIDEO_DRIVER_X11_XINPUT2 || SDL_VIDEO_DRIVER_X11_XFIXES
 #include <X11/extensions/XInput2.h>
 #endif
 #if SDL_VIDEO_DRIVER_X11_XFIXES