x86, uv: add Kconfig dependency on NUMA for UV systems

Impact: build fix

Add Kconfig dependency on NUMA for enabling UV. Although it might
be possible to configure non-NUMA UV systems, they are unsupported
and not interesting. Much of the infrastructure for UV requires
NUMA support.

Signed-off-by: Jack Steiner <steiner@sgi.com>
LKML-Reference: <20090403203942.GA20137@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>