Btrfs: kill max_extent mount option

As Yan pointed out, theres not much reason for all this complicated math to
account for file extents being split up into max_extent chunks, since they are
likely to all end up in the same leaf anyway.  Since there isn't much reason to
use max_extent, just remove the option altogether so we have one less thing we
need to test.

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -834,7 +834,6 @@ struct btrfs_fs_info {
 	u64 last_trans_log_full_commit;
 	u64 open_ioctl_trans;
 	unsigned long mount_opt;
-	u64 max_extent;
 	u64 max_inline;
 	u64 alloc_start;
 	struct btrfs_transaction *running_transaction;