hpsa: remove online devices from offline device list

When devices come on line, they should be removed from the list of
offline devices that are monitored.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Reviewed-by: Scott Teel <scott.teel@hp.com>
Reviewed-by: Joe Handzik <joseph.t.handzik@hp.com>
Reviewed by: Mike MIller <michael.miller@canonical.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>