ACPI: processor: push file static MADT pointer into internal map_madt_entry()

There's no real need for a pointer to the MADT to be global. The only
function who uses it is map_madt_entry.

This allows us to remove some more ugly #ifdefs.

Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>