btrfs: Remove tree argument from extent_writepages

It can be directly referenced from the passed address_space so do that.
No functional changes.

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

fs/btrfs/extent_io.h

@@ -411,8 +411,7 @@ int extent_invalidatepage(struct extent_io_tree *tree,
 int extent_write_full_page(struct page *page, struct writeback_control *wbc);
 int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
 			      int mode);
-int extent_writepages(struct extent_io_tree *tree,
-		      struct address_space *mapping,
+int extent_writepages(struct address_space *mapping,
 		      struct writeback_control *wbc);
 int btree_write_cache_pages(struct address_space *mapping,
 			    struct writeback_control *wbc);