staging/lustre: Remove unused functions and definitions from cl_object

cl_object_header_fini, cl_object_has_locks, cl_attr2lvb,
cl_page_list_own, cl_page_list_unmap, cl_2queue_assume,
cl_io_print, cl_enqueue,
also cleanup extern declarations in cl_object.h

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>