Btrfs: remove unused members from struct extent_state

These members are not used at all.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent_io.h

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index d6871dc..7b2f0c3 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -108,8 +108,6 @@
 	wait_queue_head_t wq;
 	atomic_t refs;
 	unsigned long state;
-	u64 split_start;
-	u64 split_end;
 
 	/* for use by the FS */
 	u64 private;