fdt: Start a test for the fdt command

Add a basic test of the 'fdt addr' command, to kick things off.

This includes a new convenience function to run a command from a printf()
string.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/cmd_ut.c b/test/cmd_ut.c
index d70b726..3789c6b 100644
--- a/test/cmd_ut.c
+++ b/test/cmd_ut.c
@@ -39,6 +39,9 @@
 #if defined(CONFIG_UT_ENV)
 	U_BOOT_CMD_MKENT(env, CONFIG_SYS_MAXARGS, 1, do_ut_env, "", ""),
 #endif
+#ifdef CONFIG_CMD_FDT
+	U_BOOT_CMD_MKENT(fdt, CONFIG_SYS_MAXARGS, 1, do_ut_fdt, "", ""),
+#endif
 #ifdef CONFIG_UT_OPTEE
 	U_BOOT_CMD_MKENT(optee, CONFIG_SYS_MAXARGS, 1, do_ut_optee, "", ""),
 #endif
@@ -131,6 +134,9 @@
 #ifdef CONFIG_UT_ENV
 	"ut env [test-name]\n"
 #endif
+#ifdef CONFIG_CMD_FDT
+	"ut fdt [test-name] - test of the fdt command\n"
+#endif
 #ifdef CONFIG_UT_LIB
 	"ut lib [test-name] - test library functions\n"
 #endif