Avoid 64 bit mod operation, which won't work on 32 bit systems.
Simple subtraction can be used instead in this case.
Reported-By: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>