- add is_multi_taskfile() to ata.h
   - initialize ata_device->multi_count with device identify data
   - use ata_pio_sectors() to support r/w multiple commands
Signed-off-by: NAlbert Lee <albertcc@tw.ibm.com>

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Signed-off-by: NJeff Garzik <jgarzik@pobox.com>