ide: add ide_pci_device_t.host_flags (take 2)

* Rename ide_pci_device_t.flags to ide_pci_device_t.host_flags
  and IDEPCI_FLAG_ISA_PORTS flag to IDE_HFLAG_ISA_PORTS.

* Add IDE_HFLAG_SINGLE flag for single channel devices.

* Convert core code and all IDE PCI drivers to use IDE_HFLAG_SINGLE
  and remove no longer needed ide_pci_device_t.channels field.

v2:
* Fix issues noticed by Sergei:
  - correct code alignment in scc_pata.c
  - s/IDE_HFLAG_SINGLE/~IDE_HFLAG_SINGLE/ in serverworks.c

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>