x86: enable ACPI extended century handling for 32bit

The extended century readout does not solve the year 2038 problem on
32bit!

v2: Fix compilation on !ACPI, pointed out by tglx

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>