nir: add initializer data to fix MSVC compile error

CC: Jason Ekstrand <jason@jlekstrand.net>
Fixes: 82799a5d1b ("nir: Add a small pass to rematerialize derefs
per-block")
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>

src/compiler/nir/nir_deref.c

@@ -481,7 +481,7 @@ rematerialize_deref_src(nir_src *src, void *_state)
 bool
 nir_rematerialize_derefs_in_use_blocks_impl(nir_function_impl *impl)
 {
-   struct rematerialize_deref_state state = { };
+   struct rematerialize_deref_state state = { 0 };
    nir_builder_init(&state.builder, impl);
 
    nir_foreach_block(block, impl) {