Drop some unused symbols from acpiphp.h and redefine SLOT_ENABLED
(which is the only slot flag now) as 1.

[rjw: Redefinition of SLOT_ENABLED, changelog]
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>