u_gralloc: assign default u_gralloc_buffer_color_info

Gralloc is the central piece to align defaults and expectations across
different APIs. Doing so simplifies client side handling. To be noted,
midpoint chroma location is preferred as the default to skip the chroma
lowering pass. The same has been suggested by all Vulkan drivers with
AHB implemented and practiced for years under venus.

Reviewed-by: Roman Stratiienko <r.stratiienko@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35613>

src/util/u_gralloc/u_gralloc.c

@@ -126,18 +126,15 @@ u_gralloc_get_buffer_color_info(struct u_gralloc *gralloc,
                                 struct u_gralloc_buffer_handle *hnd,
                                 struct u_gralloc_buffer_color_info *out)
 {
-   struct u_gralloc_buffer_color_info info = {0};
-   int ret;
+   if (gralloc->ops.get_buffer_color_info)
+      return gralloc->ops.get_buffer_color_info(gralloc, hnd, out);
 
-   if (!gralloc->ops.get_buffer_color_info)
-      return -ENOTSUP;
-
-   ret = gralloc->ops.get_buffer_color_info(gralloc, hnd, &info);
-
-   if (ret)
-      return ret;
-
-   *out = info;
+   *out = (struct u_gralloc_buffer_color_info){
+      .yuv_color_space = __DRI_YUV_COLOR_SPACE_ITU_REC601,
+      .sample_range = __DRI_YUV_NARROW_RANGE,
+      .horizontal_siting = __DRI_YUV_CHROMA_SITING_0_5,
+      .vertical_siting = __DRI_YUV_CHROMA_SITING_0_5,
+   };
 
    return 0;
 }