staging/lustre/ldlm: Remove unused interval tree bits

On client side interval-tree code operations are pretty basic,
so get rid of the code that is only used on the server to figure
out how much to extend the locks and such.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>