btrfs: reorder btrfs_inode to fill gaps

[ Upstream commit 398fb913 ]

Previous commit created a hole in struct btrfs_inode, we can move
outstanding_extents there. This reduces size by 8 bytes from 1120 to
1112 on a release config.

Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 7ee85f55 ("btrfs: fix race setting file private on concurrent lseek using same fd")
Signed-off-by: Sasha Levin <sashal@kernel.org>