tgsi: add initializer data to fix MSVC compile error

src/gallium/auxiliary/tgsi/tgsi_util.c

@@ -327,7 +327,7 @@ tgsi_util_get_inst_usage_mask(const struct tgsi_full_instruction *inst,
 struct tgsi_src_register
 tgsi_util_get_src_from_ind(const struct tgsi_ind_register *reg)
 {
-   struct tgsi_src_register src = {};
+   struct tgsi_src_register src = { 0 };
 
    src.File = reg->File;
    src.Index = reg->Index;