md/raid5: correctly update sync_completed when we reach max_resync

At the end of reshape_request we update cyrr_resync_completed
if we are about to pause due to reaching resync_max.
However we update it to the wrong value.  We need to add the
"reshape_sectors" that have just been reshaped.

Signed-off-by: NeilBrown <neilb@suse.de>