mips: bmips: enable the SPI flash on the Comtrend AR-5387un

It's a Macronix (mx25l12805d) 16 MB SPI flash.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
diff --git a/arch/mips/dts/comtrend,ar-5387un.dts b/arch/mips/dts/comtrend,ar-5387un.dts
index 73f2b49..6067881 100644
--- a/arch/mips/dts/comtrend,ar-5387un.dts
+++ b/arch/mips/dts/comtrend,ar-5387un.dts
@@ -51,6 +51,18 @@
 	};
 };
 
+&spi {
+	status = "okay";
+
+	spi-flash@0 {
+		compatible = "spi-flash";
+		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		spi-max-frequency = <33333334>;
+	};
+};
+
 &uart0 {
 	u-boot,dm-pre-reloc;
 	status = "okay";