intel/compiler: add comment about workaround on simd width

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21619>

src/intel/compiler/brw_fs_visitor.cpp

@@ -888,6 +888,12 @@ fs_visitor::emit_fb_writes()
                                 this->outputs[0].file != BAD_FILE);
    assert(!prog_data->dual_src_blend || key->nr_color_regions == 1);
 
+   /* Following condition implements Wa_14017468336:
+    *
+    * "If dual source blend is enabled do not enable SIMD32 dispatch" and
+    * "For a thread dispatched as SIMD32, must not issue SIMD8 message with Last
+    *  Render Target Select set."
+    */
    if (devinfo->ver >= 11 && devinfo->ver <= 12 &&
        prog_data->dual_src_blend) {
       /* The dual-source RT write messages fail to release the thread