x86, UV: Fix UV apic mode

Change SGI UV default apicid mode to "physical". This is
required to match settings in the UV hub chip.

Signed-off-by: Jack Steiner <steiner@sgi.com>
LKML-Reference: <20090727143856.GA8905@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>