[PATCH] acpi_pcihp: Add support for _HPX

This patch adds support for _HPX (Hot Plug Parameter Extensions)
defined in ACPI3.0a spec.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Cc: Kristen Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>