ACPI_NUMA: fix HP IA64 simulator issue with extended memory domain

ACPI 3.0 incorporated the SRAT spec, upping the table version to 2,
and extending the size of the proximity domain from 1-byte to 4-bytes.
This extension was into a reserved field that firmware should
set to 0, but the HP simulator had non-zero values there
resulting in unexpected huge numbers.

So mask the domain down to 8-bits for now.
A more general fix will be to check the table version
supplied by firmware and get paranoid about reserved fields.

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>