xsysace: simplify media change handling

Pass a struct ace_device to ace_revalidate_disk, move the media changed
check into the one caller that needs it, and give the routine a better
name.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>