ide: small ide-scan-pci.c cleanup

- ide_scan_pcibus() can become static
- instead of ide_scan_pci() we can use ide_scan_pcibus() directly
  in module_init()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>