drm: init TTM dev_mapping in ttm_bo_device_init()

With dev->anon_inode we have a global address_space ready for operation
right from the beginning. Therefore, there is no need to do a delayed
setup with TTM. Instead, set dev_mapping during initialization in
ttm_bo_device_init() and remove any "if (dev_mapping)" conditions.

Cc: Dave Airlie <airlied@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
index c18a593..8cd402c 100644
--- a/include/drm/drm_vma_manager.h
+++ b/include/drm/drm_vma_manager.h
@@ -221,8 +221,8 @@
  * @file_mapping: Address space to unmap @node from
  *
  * Unmap all userspace mappings for a given offset node. The mappings must be
- * associated with the @file_mapping address-space. If no offset exists or
- * the address-space is invalid, nothing is done.
+ * associated with the @file_mapping address-space. If no offset exists
+ * nothing is done.
  *
  * This call is unlocked. The caller must guarantee that drm_vma_offset_remove()
  * is not called on this node concurrently.
@@ -230,7 +230,7 @@
 static inline void drm_vma_node_unmap(struct drm_vma_offset_node *node,
 				      struct address_space *file_mapping)
 {
-	if (file_mapping && drm_vma_node_has_offset(node))
+	if (drm_vma_node_has_offset(node))
 		unmap_mapping_range(file_mapping,
 				    drm_vma_node_offset_addr(node),
 				    drm_vma_node_size(node) << PAGE_SHIFT, 1);