Optimise do_csum() to gang up the loads so they're less likely to get
interruptions between.
Signed-off-by: NAkira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: NKiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>