mesa/program: Switch ir_to_mesa_instruction to the non-zeroing allocator.

All member variables of ir_to_mesa_instruction are already being
initialized from its implicitly defined constructor, it's not
necessary to use rzalloc to allocate its memory.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/program/ir_to_mesa.cpp

@@ -155,7 +155,7 @@ namespace {
 
 class ir_to_mesa_instruction : public exec_node {
 public:
-   DECLARE_RZALLOC_CXX_OPERATORS(ir_to_mesa_instruction)
+   DECLARE_RALLOC_CXX_OPERATORS(ir_to_mesa_instruction)
 
    enum prog_opcode op;
    dst_reg dst;