[PATCH] libata irq-pio: misc fixes

   - ata_pio_block(): add ata_altstatus(ap) to prevent reading device status before it is valid
   - remove the unnecessary HSM_ST_IDLE state from ata_pio_task()
   - raise BUG() when unknown state is found in ata_pio_task()

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>

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