asahi: static assert blend key size

need to make sure it's padded because C

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28483>

src/gallium/drivers/asahi/agx_state.h

@@ -454,7 +454,9 @@ struct agx_blend_key {
    nir_lower_blend_rt rt[8];
    unsigned logicop_func;
    bool alpha_to_coverage, alpha_to_one;
+   bool padding[2];
 };
+static_assert(sizeof(struct agx_blend_key) == 232, "packed");
 
 struct agx_blend {
    struct agx_blend_key key;