Staging: VME: Fix Universe II int ack logic.

The driver must acknowledge the interrupts that have been actually serviced, not
the ones active. The current code could acknowledge an interrupt that has not
been serviced at all.

Signed-off-by: Vincent Bossier <vincent.bossier@gmail.com>
Acked-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>