dfu: dfu_sf: use correct print code

For printing unsigned int %u has to be used.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/drivers/dfu/dfu_sf.c b/drivers/dfu/dfu_sf.c
index 318e43c..76b629a 100644
--- a/drivers/dfu/dfu_sf.c
+++ b/drivers/dfu/dfu_sf.c
@@ -131,7 +131,7 @@
 
 	dev = spi_flash_probe(bus, cs, speed, mode);
 	if (!dev) {
-		printf("Failed to create SPI flash at %d:%d:%d:%d\n",
+		printf("Failed to create SPI flash at %u:%u:%u:%u\n",
 		       bus, cs, speed, mode);
 		return NULL;
 	}