ide: add IDE_HFLAG_{IO_32BIT,UNMASK_IRQS} host flags

Add IDE_HFLAG_{IO_32BIT,UNMASK_IRQS} host flag to tell ide_pci_setup_ports()
to set drive->{io_32bit,unmask} for both drives on the interface.  Convert
amd74xx, sl82c105 and via82cxxx host drivers to use these new host flags.

While at it:

* Add IDE_HFLAGS_AMD define (amd74xx host driver).

* Add IDE_HFLAGS_VIA define (via82cxxx host driver).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>