pan/bi: Add bifrost_minmax_mode field

We'll open up a union for class specific data, since this is interesting
only to BI_MINMAX. (And even then...)

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4061>
diff --git a/src/panfrost/bifrost/compiler.h b/src/panfrost/bifrost/compiler.h
index 421db9a..97c6d06 100644
--- a/src/panfrost/bifrost/compiler.h
+++ b/src/panfrost/bifrost/compiler.h
@@ -106,6 +106,11 @@
 
         /* Round mode (requires BI_ROUNDMODE) */
         enum bifrost_roundmode roundmode;
+
+        /* Union for class-specific information */
+        union {
+                enum bifrost_minmax_mode minmax;
+        };
 } bi_instruction;
 
 typedef struct {