[PATCH] libata: let ATA_FLAG_PIO_POLLING use polling pio for ATA_PROT_NODATA

Even if ATA_FLAG_PIO_POLLING is set, libata uses irq pio for the ATA_PROT_NODATA protocol.
This patch let ATA_FLAG_PIO_POLLING use polling pio for the ATA_PROT_NODATA protocol.

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>