ir: rip out special logic for using addr-of instruction for types

See #588

Author: andrewrk

src/all_types.hpp

@@ -2275,8 +2275,6 @@ struct IrInstructionVarPtr {
     IrInstruction base;
 
     VariableTableEntry *var;
-    bool is_const;
-    bool is_volatile;
 };
 
 struct IrInstructionCall {