x86, ioapic: Early enable ioapic for timer irq

Moorestown platform needs apic ready early for the system timer irq
which is delievered via ioapic.  Should not impact other platforms.

In the longer term, once ioapic setup is moved before late time init,
we will not need this patch to do early apic enabling.

Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80D07@orsmsx508.amr.corp.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>