cciss: Add enhanced scatter-gather support.  For controllers which
supported, more than 512 scatter-gather elements per command may
be used, and the max transfer size can be increased to 8192 blocks.
Signed-off-by: NDon Brace <brace@beardog.cce.hp.com>
Signed-off-by: NStephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>