ide-scsi: fix DRQ checking for DMA transfers in idescsi_pc_intr()

If DRQ bit of Status Register is not cleared it is an error condition
and should be handled accordingly (disable DMA + reset the device).

Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>