pan/bi: Use IMATH for nir_op_iadd

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4890>
diff --git a/src/panfrost/bifrost/compiler.h b/src/panfrost/bifrost/compiler.h
index 3b54c48..eb0c4d1 100644
--- a/src/panfrost/bifrost/compiler.h
+++ b/src/panfrost/bifrost/compiler.h
@@ -167,6 +167,11 @@
         BI_BITWISE_XOR
 };
 
+enum bi_imath_op {
+        BI_IMATH_ADD,
+        BI_IMATH_SUB,
+};
+
 enum bi_table_op {
         /* fp32 log2() with low precision, suitable for GL or half_log2() in
          * CL. In the first argument, takes x. Letting u be such that x =
@@ -276,6 +281,7 @@
                 enum bi_table_op table;
                 enum bi_frexp_op frexp;
                 enum bi_tex_op texture;
+                enum bi_imath_op imath;
 
                 /* For FMA/ADD, should we add a biased exponent? */
                 bool mscale;