gallium glsl: Fix crash with piglit fs-deref-literal-array-of-structs.shader_test

This allows the following shader code to work without a weird crash:

struct Foo {
  int value[1];
};

int actual_value = Foo[2](Foo(int[1](100)), Foo(int[1](200)))[i].value[0];

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -632,7 +632,10 @@ glsl_to_tgsi_visitor::get_opcode(ir_instruction *ir, unsigned op,
         		 st_src_reg src0, st_src_reg src1)
 {
    int type = GLSL_TYPE_FLOAT;
-   
+
+   if (op == TGSI_OPCODE_MOV)
+       return op;
+
    assert(src0.type != GLSL_TYPE_ARRAY);
    assert(src0.type != GLSL_TYPE_STRUCT);
    assert(src1.type != GLSL_TYPE_ARRAY);