sata_promise uses two different command modes - packet and TF.  Packet mode
is intelligent low-overhead mode while TF is the same old taskfile
interface.  As with other advanced interface (ahci/sil24),
ATA_TFLAG_POLLING has no effect in packet mode.  However, PIO commands are
issued using TF interface in polling mode, so pdc_interrupt() considers
interrupts spurious if ATA_TFLAG_POLLING is set.

This is broken for polling NODATA commands because command is issued using
packet mode but the interrupt handler ignores it due to ATA_TFLAG_POLLING.
Fix pdc_qc_issue_prot() such that ATA/ATAPI NODATA commands are issued
using TF interface if ATA_TFLAG_POLLING is set.

This patch fixes detection failure introduced by polling SETXFERMODE.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Mikael Pettersson <mikpe@it.uu.se>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>