drm/exynos: Set fbdev FBINFO_VIRTFB flag

Mark the framebuffer with FBINFO_VIRTFB. The framebuffer range is
in DMA-able memory and should be accessed with the CPU's regular
memory ops.

v2:
	* drop FBINFO_FLAG_DEFAULT

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by : Inki Dae <inki.dae@samsung.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230707083422.18691-8-tzimmermann@suse.de

Author: tdz

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

@@ -79,6 +79,7 @@ static int exynos_drm_fbdev_update(struct drm_fb_helper *helper,
 	offset = fbi->var.xoffset * fb->format->cpp[0];
 	offset += fbi->var.yoffset * fb->pitches[0];
 
+	fbi->flags |= FBINFO_VIRTFB;
 	fbi->screen_buffer = exynos_gem->kvaddr + offset;
 	fbi->screen_size = size;
 	fbi->fix.smem_len = size;