x86, pci: Add arch_init to x86_init abstraction

Added an abstraction function for arch specific init calls.

Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
LKML-Reference: <43F901BD926A4E43B106BF17856F0755A318CE84@orsmsx508.amr.corp.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>