ide: fix ide_find_port()

* Instead of checking for '->io_ports[IDE_DATA_OFFSET] == 0' check for
  '->chipset == ide_unknown' when looking for an empty ide_hwifs[] slot.

* Do ide-pnp initialization after ide-generic when IDE is built-in
  (ide-pnp is the only user of ide_find_port() which needs such fixup).

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