rockchip: Enable building a SPI ROM image on bob

Add a simple binman config and enable CONFIG_HAS_ROM so that U-Boot
produces a ROM for bob.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/rk3399-gru.dtsi b/arch/arm/dts/rk3399-gru.dtsi
index 7ac8839..f9c5bb6 100644
--- a/arch/arm/dts/rk3399-gru.dtsi
+++ b/arch/arm/dts/rk3399-gru.dtsi
@@ -537,7 +537,7 @@
 	pinctrl-names = "default", "sleep";
 	pinctrl-1 = <&spi1_sleep>;
 
-	spiflash@0 {
+	spi_flash: spiflash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;