venus: advertise the VK_EXT_custom_border_color extension

Allows the extension passthrough.

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
Signed-off-by: Igor Torrente <igor.torrente@collabora.com>

src/venus/vkr_common.c

@@ -93,6 +93,7 @@ static const struct vn_info_extension_table vkr_extension_table = {
    /* KHR extensions */
    .KHR_external_memory_fd = true,
    /* EXT extensions */
+   .EXT_custom_border_color = true,
    .EXT_external_memory_dma_buf = true,
    .EXT_image_drm_format_modifier = true,
    .EXT_queue_family_foreign = true,