x86, uv: add early detection of UV system types

Portions of the ACPI code needs to know if a system is a UV system prior
to genapic initialization. This patch adds a call early_acpi_boot_init()
so that the apic type is discovered earlier.

V2 of the patch adding fixes from Yinghai Lu.
Much cleaner and smaller.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>