drm/exynos: atomic phase 2: keep track of framebuffer pointer

Use drm_atomic_set_fb_for_plane() in the legacy page_flip path to keep
track of the framebuffer pointer and reference.
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Joonyoung Shim <jy0922.shim@samsung.com>
Tested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_crtc.c

@@ -168,6 +168,9 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 			    crtc_w, crtc_h, crtc->x << 16, crtc->y << 16,
 			    crtc_w << 16, crtc_h << 16);
 
+	if (crtc->primary->state)
+		drm_atomic_set_fb_for_plane(crtc->primary->state, fb);
+
 	return 0;
 
 out: