ARM: dts: rmobile: Force 1-bit bus width on Gen2 QSPI

U-Boot currently uses Gen2 QSPI in 1-bit mode, enforce it until
we can do better using the new SPI NOR framework.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/arch/arm/dts/r8a7791-koelsch-u-boot.dts b/arch/arm/dts/r8a7791-koelsch-u-boot.dts
index 85a5290..4a98528 100644
--- a/arch/arm/dts/r8a7791-koelsch-u-boot.dts
+++ b/arch/arm/dts/r8a7791-koelsch-u-boot.dts
@@ -11,3 +11,10 @@
 &scif0 {
 	u-boot,dm-pre-reloc;
 };
+
+&qspi {
+	flash@0 {
+		spi-tx-bus-width = <1>;
+		spi-rx-bus-width = <1>;
+	};
+};