btrfs: make clear_extent_buffer_uptodate return void

Does not return any errors, nor anything from the callgraph.

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.h

@@ -331,7 +331,7 @@ void memset_extent_buffer(struct extent_buffer *eb, char c,
 void clear_extent_buffer_dirty(struct extent_buffer *eb);
 int set_extent_buffer_dirty(struct extent_buffer *eb);
 void set_extent_buffer_uptodate(struct extent_buffer *eb);
-int clear_extent_buffer_uptodate(struct extent_buffer *eb);
+void clear_extent_buffer_uptodate(struct extent_buffer *eb);
 int extent_buffer_uptodate(struct extent_buffer *eb);
 int extent_buffer_under_io(struct extent_buffer *eb);
 int map_private_extent_buffer(struct extent_buffer *eb, unsigned long offset,