advansys: remove ISA support

This is the last piece in the kernel requiring the block layer ISA
bounce buffering, and it does not actually look used.  So remove it
to see if anyone screams, in which case we'll need to find a solution
to fix it back up.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210331073001.46776-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>