ide: make remaining built-in only IDE host drivers modular (take 2)

* Make remaining built-in only IDE host drivers modular, add ide-scan-pci.c
  file for probing PCI host drivers registered with IDE core (special case
  for built-in IDE and CONFIG_IDEPCI_PCIBUS_ORDER=y) and then take care of
  the ordering in which all IDE host drivers are probed when IDE is built-in
  during link time.

* Move probing of gayle, falconide, macide, q40ide and buddha (m68k arch
  specific) host drivers, before PCI ones (no PCI on m68k), ide-cris (cris
  arch specific), cmd640 (x86 arch specific) and pmac (ppc arch specific).

* Move probing of ide-cris (cris arch specific) host driver before cmd640
  (x86 arch specific).

* Move probing of mpc8xx (ppc specific) host driver before ide-pnp (depends
  on ISA and none of ppc platform that use mpc8xx supports ISA) and ide-h8300
  (h8300 arch specific).

* Add "probe_vlb" kernel parameter to cmd640 host driver and update
  Documentation/ide.txt accordingly.

* Make IDE_ARM config option visible so it can also be disabled if needed.

* Remove bogus comment from ide.c while at it.

v2:
* Fix two issues spotted by Sergei:
  - replace ENOMEM error value by ENOENT in ide-h8300 host driver
  - fix MODULE_PARM_DESC() in cmd640 host driver

Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>