acpiphp: Execute ACPI _REG method for hotadded devices

Per ACPI spec, _ERG method should be executed before device driver
gets control for hotpluged device. Firmware might do some configuration
there. See http://bugzilla.kernel.org/show_bug.cgi?id=10805. In this
machine, _REG method of docked device will configure cardbus bridge.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Tested-by: Paul Martin <pm@debian.org>
Signed-off-by: Len Brown <len.brown@intel.com>