staging/lustre: Remove OBD_CPT_ALLOC_LARGE

Remove OBD_CPT_ALLOC_LARGE define and convert the only user to
libcfs_kvzalloc_cpt.

Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>