btrfs: update i_version in update_dev_time

When updating the ctime, we also want to update i_version.

This is just something I noticed by inspection. There is probably no way
to test this today unless you can somehow get to this inode via nfsd.
Still, I think it's the right thing to do for consistency's sake.

David Sterba's comment: I don't see anything wrong with setting the
iversion bit, however I also don't see where this would be useful.
Agreed with the consistency, otherwise the time is updated when device
super block is wiped or a device initialized, both are big events so
missing that due to lack of iversion update seems unlikely. I'll add it
to the queue, thanks.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
[ add comments ]
Signed-off-by: David Sterba <dsterba@suse.com>