drm/shmem: Cleanup drm_gem_shmem_create_with_handle()

Once we create the handle, the handle owns the reference.  Currently
nothing was doing anything with the shmem ptr after the handle was
created, but let's change drm_gem_shmem_create_with_handle() to not
return the pointer, so-as to not encourage problematic use of this
function in the future.  As a bonus, it makes the code a bit cleaner.

Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/drm_gem_shmem_helper.c

@@ -415,7 +415,7 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
 }
 EXPORT_SYMBOL(drm_gem_shmem_vunmap);
 
-static struct drm_gem_shmem_object *
+static int
 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
 				 struct drm_device *dev, size_t size,
 				 uint32_t *handle)
@@ -434,10 +434,8 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
 	ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
 	/* drop reference from allocate - handle holds it now. */
 	drm_gem_object_put(&shmem->base);
-	if (ret)
-		return ERR_PTR(ret);
 
-	return shmem;
+	return ret;
 }
 
 /* Update madvise status, returns true if not purged, else
@@ -533,9 +531,7 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
 			args->size = PAGE_ALIGN(args->pitch * args->height);
 	}
 
-	shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
-
-	return PTR_ERR_OR_ZERO(shmem);
+	return drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);