glsl: Initialize lod_info in the ir_texture constructor.

This isn't strictly necessary, since creators of ir_texture objects
should set LOD when relevant.  However, it's nice to have a NULL pointer
in case they forget.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/glsl/ir.h

@@ -1568,6 +1568,7 @@ public:
         shadow_comparitor(NULL), offset(NULL)
    {
       this->ir_type = ir_type_texture;
+      memset(&lod_info, 0, sizeof(lod_info));
    }
 
    virtual ir_texture *clone(void *mem_ctx, struct hash_table *) const;