ACPICA: Add namespace node to operand object union

Add ACPI_NAMESPACE_NODE to the ACPI_OPERAND_OBJECT in order to
simplify code that accepts both of these objects. A common type
field is used to differentiate them.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>