drm/tiny/gm12u320: Use fbdev-shmem

Implement fbdev emulation with fbdev-shmem. Avoids the overhead of
fbdev-generic's additional shadow buffering. No functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-16-tzimmermann@suse.de

drivers/gpu/drm/tiny/gm12u320.c

@@ -13,7 +13,7 @@
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_edid.h>
-#include <drm/drm_fbdev_generic.h>
+#include <drm/drm_fbdev_shmem.h>
 #include <drm/drm_file.h>
 #include <drm/drm_format_helper.h>
 #include <drm/drm_fourcc.h>
@@ -699,7 +699,7 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
 	if (ret)
 		goto err_put_device;
 
-	drm_fbdev_generic_setup(dev, 0);
+	drm_fbdev_shmem_setup(dev, 0);
 
 	return 0;