arm64: dts: imx8mq-u-boot.dtsi: explicitly add spl filename

Explicitly add SPL aka u-boot-spl.bin filename.

Signed-off-by: Patrick Wildt <patrick@blueri.se>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/arch/arm/dts/imx8mq-u-boot.dtsi b/arch/arm/dts/imx8mq-u-boot.dtsi
index d8208ae..566b8b8 100644
--- a/arch/arm/dts/imx8mq-u-boot.dtsi
+++ b/arch/arm/dts/imx8mq-u-boot.dtsi
@@ -19,6 +19,7 @@
 
 		u-boot-spl {
 			align-end = <4>;
+			filename = "u-boot-spl.bin";
 		};
 
 		blob_1: blob-ext@1 {