x86: uv cleanup, build fix

Fix:

 arch/x86/mm/srat_64.c: In function ‘acpi_numa_processor_affinity_init’:
 arch/x86/mm/srat_64.c:141: error: implicit declaration of function ‘get_uv_system_type’
 arch/x86/mm/srat_64.c:141: error: ‘UV_X2APIC’ undeclared (first use in this function)
 arch/x86/mm/srat_64.c:141: error: (Each undeclared identifier is reported only once
 arch/x86/mm/srat_64.c:141: error: for each function it appears in.)

A couple of UV definitions were moved to asm/uv/uv.h, but srat_64.c did
not include that header. Add it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>