ACPICA: Removed unused code

Handling of AML_NAME_OP as a Reference.Opcode is no longer
needed. Kernel bugzilla 2874

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>