intel/isl: add blend enable flag to gen4/5

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10655>

src/intel/isl/isl.h

@@ -1422,6 +1422,11 @@ struct isl_surf_fill_state_info {
     */
    isl_channel_mask_t write_disables;
 
+   /**
+    * blend enable for gfx4-5
+    */
+   bool blend_enable;
+
    /* Intra-tile offset */
    uint16_t x_offset_sa, y_offset_sa;
 };

src/intel/isl/isl_surface_state.c

@@ -320,6 +320,7 @@ isl_genX(surf_fill_state_s)(const struct isl_device *dev, void *state,
 
 #if GFX_VER <= 5
    s.ColorBufferComponentWriteDisables = info->write_disables;
+   s.ColorBlendEnable = info->blend_enable;
 #else
    assert(info->write_disables == 0);
 #endif