kmsdrm: If async page flip fails, try again without the async flag.

Fixes #16174.

(manually cherry picked from commit 69dd29eec2fc12d02e8a05b2fbba2d1cd03c1531)

src/video/kmsdrm/SDL_kmsdrmopengles.c

diff --git a/src/video/kmsdrm/SDL_kmsdrmopengles.c b/src/video/kmsdrm/SDL_kmsdrmopengles.c
index 3b17639..fc55880 100644
--- a/src/video/kmsdrm/SDL_kmsdrmopengles.c
+++ b/src/video/kmsdrm/SDL_kmsdrmopengles.c
@@ -181,6 +181,14 @@
         ret = KMSDRM_drmModePageFlip(viddata->drm_fd, dispdata->crtc->crtc_id,
                                      fb_info->fb_id, flip_flags, &windata->waiting_for_flip);
 
+        /* some drivers apparently claim they can do async page flip but can't (or have intermittent problems),
+           so in this specific case just retry without the async flag. If it still fails after that, oh well. */
+        if ((ret == -EINVAL) && (flip_flags & DRM_MODE_PAGE_FLIP_ASYNC)) {
+            flip_flags &= ~DRM_MODE_PAGE_FLIP_ASYNC;
+            ret = KMSDRM_drmModePageFlip(viddata->drm_fd, dispdata->crtc->crtc_id,
+                                         fb_info->fb_id, flip_flags, &windata->waiting_for_flip);
+        }
+
         if (ret == 0) {
             windata->waiting_for_flip = SDL_TRUE;
         } else {