test/dm: add sandbox test for sysinfo_get_data

Adding sysinfo_get_data into sandbox ut test dm_test_sysinfo.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
diff --git a/drivers/sysinfo/sandbox.h b/drivers/sysinfo/sandbox.h
index a7cbac0..47b7f5e 100644
--- a/drivers/sysinfo/sandbox.h
+++ b/drivers/sysinfo/sandbox.h
@@ -9,4 +9,5 @@
 	INT_TEST1,
 	INT_TEST2,
 	STR_VACATIONSPOT,
+	DATA_TEST,
 };