drm/vc4: bo: Fix unused variable warning

Commit 07a2975 ("drm/vc4: bo: Fix drmm_mutex_init memory hog")
removed the only use of the ret variable, but didn't remove the
variable itself leading to a unused variable warning.

Remove that variable.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 07a2975 ("drm/vc4: bo: Fix drmm_mutex_init memory hog")
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230113154637.1704116-1-maxime@cerno.tech

Author: mripard

drivers/gpu/drm/vc4/vc4_bo.c

@@ -395,7 +395,6 @@ struct drm_gem_object *vc4_create_object(struct drm_device *dev, size_t size)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct vc4_bo *bo;
-	int ret;
 
 	if (WARN_ON_ONCE(vc4->is_vc5))
 		return ERR_PTR(-ENODEV);