imx: image: use 'u-boot-dtb.img' filename for SPL payload

For targets in U-Boot which were migrated to DM, the correct binary
image filename will be 'u-boot-dtb.img'. For backward compatibility,
keep support for both files and use the one which was generated with
our 'uboot-imx' package.

See also 'CONFIG_SPL_FS_LOAD_PAYLOAD_NAME' and 'CONFIG_OF_CONTROL' in
mainline U-Boot sources.

Signed-off-by: Piotr Dymacz <[email protected]>

target/linux/imx/image/cortexa9.mk

@@ -80,7 +80,16 @@ endef
 define Build/imx6-sdcard
 	$(Build/imx6-combined-image-prepare)
 
-	$(CP) $(STAGING_DIR_IMAGE)/$(UBOOT)-u-boot.img [email protected]/u-boot.img
+	if [ -f $(STAGING_DIR_IMAGE)/$(UBOOT)-u-boot.img ]; then \
+		$(CP) $(STAGING_DIR_IMAGE)/$(UBOOT)-u-boot.img \
+		[email protected]/u-boot.img; \
+	fi
+
+	if [ -f $(STAGING_DIR_IMAGE)/$(UBOOT)-u-boot-dtb.img ]; then \
+		$(CP) $(STAGING_DIR_IMAGE)/$(UBOOT)-u-boot-dtb.img \
+		[email protected]/u-boot-dtb.img; \
+	fi
+
 	$(Build/imx6-combined-image)
 	dd if=$(STAGING_DIR_IMAGE)/$(UBOOT)-SPL of=$@ bs=1024 seek=1 conv=notrunc