Patch merged into coreboot/master: arch/acpi.h: add #if guard to handle the absence of device_t type

the following patch was just integrated into master:
commit 20c9afa9c7035d102f2ce102ffe23e86ca520242
Author: Antonello Dettori 
Date:   Fri Sep 2 09:08:01 2016 +0200

arch/acpi.h: add #if guard to handle the absence of device_t type

Avoid the inclusion of a function declaration if the argument type
    device_t is not defined.

This was not a problem until now because the
    old declaration of device_t and the new one overlapped.

Change-Id: I05a6ef1bf65bf47f3c6933073ae2d26992348813
    Signed-off-by: Antonello Dettori 
    Reviewed-on: https://review.coreboot.org/16404
    Tested-by: build bot (Jenkins)
    Reviewed-by: Martin Roth

See https://review.coreboot.org/16404 for details.

-gerrit