drm/repaper: Drop explicit drm_mode_config_cleanup call

Allows us to drop the drm_driver.release callback.

This is made possible by a preceeding patch which added a drmm_
cleanup action to drm_mode_config_init(), hence all we need to do to
ensure that drm_mode_config_cleanup() is run on final drm_device
cleanup is check the new error code for _init().

v2: Explain why this cleanup is possible (Laurent).

v3: Use drmm_mode_config_init() for more clarity (Sam, Thomas)
I also noticed that I've failed to add the error checking,
__must_check caught that.

Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org> (v2)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-47-daniel.vetter@ffwll.ch

drivers/gpu/drm/tiny/repaper.c

@@ -909,13 +909,6 @@ static const struct drm_mode_config_funcs repaper_mode_config_funcs = {
 	.atomic_commit = drm_atomic_helper_commit,
 };
 
-static void repaper_release(struct drm_device *drm)
-{
-	DRM_DEBUG_DRIVER("\n");
-
-	drm_mode_config_cleanup(drm);
-}
-
 static const uint32_t repaper_formats[] = {
 	DRM_FORMAT_XRGB8888,
 };
@@ -953,7 +946,6 @@ DEFINE_DRM_GEM_CMA_FOPS(repaper_fops);
 static struct drm_driver repaper_driver = {
 	.driver_features	= DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
 	.fops			= &repaper_fops,
-	.release		= repaper_release,
 	DRM_GEM_CMA_VMAP_DRIVER_OPS,
 	.name			= "repaper",
 	.desc			= "Pervasive Displays RePaper e-ink panels",
@@ -1023,7 +1015,9 @@ static int repaper_probe(struct spi_device *spi)
 	}
 	drmm_add_final_kfree(drm, epd);
 
-	drm_mode_config_init(drm);
+	ret = drmm_mode_config_init(drm);
+	if (ret)
+		return ret;
 	drm->mode_config.funcs = &repaper_mode_config_funcs;
 
 	epd->spi = spi;