[DLM] fix i_private

> I think you must have an old version of the base kernel as well?
> i_private no longer exists in struct inode, so you'll have to use
> something else,

I have that patch in my stack but didn't send it; for some reason I
thought it was already changed in your git tree.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>