egl: Protect use of gbm_dri with ifdef HAVE_DRM_PLATFORM

Otherwise it fails to compile if the drm egl platform is disabled.

Cc: "10.0" "10.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
(cherry picked from commit 17860309f1)

src/egl/drivers/dri2/egl_dri2.c

@@ -1892,10 +1892,12 @@ dri2_bind_wayland_display_wl(_EGLDriver *drv, _EGLDisplay *disp,
    if (!dri2_dpy->wl_server_drm)
 	   return EGL_FALSE;
 
+#ifdef HAVE_DRM_PLATFORM
    /* We have to share the wl_drm instance with gbm, so gbm can convert
     * wl_buffers to gbm bos. */
    if (dri2_dpy->gbm_dri)
       dri2_dpy->gbm_dri->wl_drm = dri2_dpy->wl_server_drm;
+#endif
 
    return EGL_TRUE;
 }