pan/bi: Add CSEL condition

Along with src_types, this is enough to represent CSEL.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4061>

src/panfrost/bifrost/compiler.h

@@ -234,6 +234,10 @@ typedef struct {
                 struct bi_load load;
                 struct bi_load_vary load_vary;
                 struct bi_branch branch;
+
+                /* For CSEL, the comparison op. BI_COND_ALWAYS doesn't make
+                 * sense here but you can always just use a move for that */
+                enum bi_cond csel_cond;
         };
 } bi_instruction;