dm: test: Add a test for the LED uclass

Add a test to confirm that we can adjust LEDs using the led_gpio driver.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/Makefile b/test/dm/Makefile
index 54046d3..6242a02 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -19,6 +19,7 @@
 obj-$(CONFIG_DM_ETH) += eth.o
 obj-$(CONFIG_DM_GPIO) += gpio.o
 obj-$(CONFIG_DM_I2C) += i2c.o
+obj-$(CONFIG_LED) += led.o
 obj-$(CONFIG_DM_MMC) += mmc.o
 obj-$(CONFIG_DM_PCI) += pci.o
 obj-$(CONFIG_RAM) += ram.o