dm: sf: Update default name of spi flash in structure udevice

Default name of spi flash like this "0:0", update it to "spi_flash@0:0".

Signed-off-by: Haikun Wang <haikun.wang@freescale.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/spi/sf-uclass.c b/drivers/mtd/spi/sf-uclass.c
index 4b25902..350e21a 100644
--- a/drivers/mtd/spi/sf-uclass.c
+++ b/drivers/mtd/spi/sf-uclass.c
@@ -53,10 +53,10 @@
 {
 	struct spi_slave *slave;
 	struct udevice *bus;
-	char name[20], *str;
+	char name[30], *str;
 	int ret;
 
-	snprintf(name, sizeof(name), "%d:%d", busnum, cs);
+	snprintf(name, sizeof(name), "spi_flash@%d:%d", busnum, cs);
 	str = strdup(name);
 	ret = spi_get_bus_and_cs(busnum, cs, max_hz, spi_mode,
 				  "spi_flash_std", str, &bus, &slave);