[IA64] Cleanup acpi header to reuse the generic _PDC defines

ia64 _PDC setup is defined similar to i386. So, cleanup the header to use
generic _PDC defines than using specific defines in ia64.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>