ide: add IDE_HFLAG_MMIO host flag (take 2)

* Add IDE_HFLAG_MMIO host flag and set it for hosts which use
  default_hwif_mmiops().

v2:
* Fix kernel panic in pmac host driver (',' should be '|').

  Thanks to Kamalesh for reporting it + testing the fix
  and to Andrew for hinting me about the source of the issue.

Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>