virgl_hw: add a warning noting the bool_set1 is full

There are 32 members in this now, so don't add anything more to it.

Reviewed-by: Elie Tournier <elie.tournier@collabora.com>

src/virgl_hw.h

@@ -242,6 +242,7 @@ struct virgl_caps_bool_set1 {
         unsigned derivative_control:1;
         unsigned polygon_offset_clamp:1;
         unsigned transform_feedback_overflow_query:1;
+        /* DO NOT ADD ANYMORE MEMBERS - need to add another 32-bit to v2 caps */
 };
 
 /* endless expansion capabilites - current gallium has 252 formats */