Revert "drm/panfrost: Use drm_gem_map_offset()"

This reverts commit 583bbf46.

Turns out we need mmap to work on imported BOs even if the current code
is buggy.
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/gpu/drm/panfrost/panfrost_drv.c

@@ -259,14 +259,26 @@ static int panfrost_ioctl_mmap_bo(struct drm_device *dev, void *data,
 		      struct drm_file *file_priv)
 {
 	struct drm_panfrost_mmap_bo *args = data;
+	struct drm_gem_object *gem_obj;
+	int ret;
 
 	if (args->flags != 0) {
 		DRM_INFO("unknown mmap_bo flags: %d\n", args->flags);
 		return -EINVAL;
 	}
 
-	return drm_gem_map_offset(file_priv, dev, args->handle,
-				       &args->offset);
+	gem_obj = drm_gem_object_lookup(file_priv, args->handle);
+	if (!gem_obj) {
+		DRM_DEBUG("Failed to look up GEM BO %d\n", args->handle);
+		return -ENOENT;
+	}
+
+	ret = drm_gem_create_mmap_offset(gem_obj);
+	if (ret == 0)
+		args->offset = drm_vma_node_offset_addr(&gem_obj->vma_node);
+	drm_gem_object_put_unlocked(gem_obj);
+
+	return ret;
 }
 
 static int panfrost_ioctl_get_bo_offset(struct drm_device *dev, void *data,