Fixed bug 5543 - Wayland: Fix waylandvideo.h warnings

wahil1976

This patch fixes the warnings seen when compiling the Wayland backend. This will also be required in the future to avoid issues with compilation.
diff --git a/src/video/wayland/SDL_waylandvideo.h b/src/video/wayland/SDL_waylandvideo.h
index 3549474..e4b865d 100644
--- a/src/video/wayland/SDL_waylandvideo.h
+++ b/src/video/wayland/SDL_waylandvideo.h
@@ -35,6 +35,7 @@
 */
 
 #define MESA_EGL_NO_X11_HEADERS
+#define EGL_NO_X11
 #include <EGL/egl.h>
 #include "wayland-util.h"