Staging: lustre: obdclass: Declare lu_site_hash_ops as static

lu_site_hash_ops is used only in this particular file. Thus declare
it as static.

Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>