test: bootcount: add bootcount-uclass test

Add a test for the bootcount uclass, which uses the RTC bootcount backend
(i.e. drivers/bootcount/rtc.c is implictly also tested).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/Makefile b/test/dm/Makefile
index 7dc80be..1b08996 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -15,6 +15,7 @@
 obj-$(CONFIG_SOUND) += audio.o
 obj-$(CONFIG_BLK) += blk.o
 obj-$(CONFIG_BOARD) += board.o
+obj-$(CONFIG_DM_BOOTCOUNT) += bootcount.o
 obj-$(CONFIG_CLK) += clk.o
 obj-$(CONFIG_DM_ETH) += eth.o
 obj-$(CONFIG_FIRMWARE) += firmware.o