drm/vgem: Use drmm_add_final_kfree

With this we can drop the final kfree from the release function.

v2: After drm_dev_init/drmm_add_final_kfree we need to clean up
everything through a drm_dev_put. Rework the unwind code to match
that.
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: Rob Clark <robdclark@chromium.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-14-daniel.vetter@ffwll.ch

drivers/gpu/drm/vgem/vgem_drv.c

@@ -39,6 +39,7 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_ioctl.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_prime.h>
 
 #include "vgem_drv.h"
@@ -432,8 +433,6 @@ static void vgem_release(struct drm_device *dev)
 
 	platform_device_unregister(vgem->platform);
 	drm_dev_fini(&vgem->drm);
-
-	kfree(vgem);
 }
 
 static struct drm_driver vgem_driver = {
@@ -489,16 +488,19 @@ static int __init vgem_init(void)
 			   &vgem_device->platform->dev);
 	if (ret)
 		goto out_unregister;
+	drmm_add_final_kfree(&vgem_device->drm, vgem_device);
 
 	/* Final step: expose the device/driver to userspace */
 	ret = drm_dev_register(&vgem_device->drm, 0);
 	if (ret)
-		goto out_fini;
+		goto out_put;
 
 	return 0;
 
-out_fini:
-	drm_dev_fini(&vgem_device->drm);
+out_put:
+	drm_dev_put(&vgem_device->drm);
+	return ret;
+
 out_unregister:
 	platform_device_unregister(vgem_device->platform);
 out_free: