scsi: aacraid: use scsi_host_(block,unblock) to block I/O

scsi: aacraid: use scsi_host_(block,unblock) to block I/O

Use scsi_host_block() and scsi_host_unblock() instead of
scsi_block_requests()/scsi_unblock_requests() to block and unblock I/O.
This has the advantage that the block layer will stop sending I/O to the
adapter instead of having the SCSI midlayer requeueing I/O internally.

Link: https://lore.kernel.org/r/20200228075318.91255-10-hare@suse.de
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Balsundar P < Balsundar.P@microchip.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>