Btrfs: remove no longer used logged range variables when logging extents

Btrfs: remove no longer used logged range variables when logging extents

The logged_start and logged_end variables, at btrfs_log_changed_extents,
were added in commit b7a0d5f83580 ("btrfs: log csums for all modified
extents"). However since the recent simplification for fsync, which makes
us wait for all ordered extents to complete before logging extents, we
no longer need those variables. Commit 5b3f708e964b ("btrfs: clean up the
left over logged_list usage") forgot to remove them.

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