test: Run bootstd tests only on sandbox

These make use of disk images which are not available on reak boards.
Add a new Kconfig to ensure these tests only run where they are valid.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/Kconfig b/test/Kconfig
index 310fb1b..e842c01 100644
--- a/test/Kconfig
+++ b/test/Kconfig
@@ -65,6 +65,11 @@
 
 endif
 
+config UT_BOOTSTD
+	bool "Unit tests for standard boot"
+	depends on UNIT_TEST && SANDBOX
+	default y
+
 config UT_COMPRESSION
 	bool "Unit test for compression"
 	depends on UNIT_TEST
diff --git a/test/Makefile b/test/Makefile
index 8e1fed2..6b8a150 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -23,7 +23,7 @@
 obj-y += ut.o
 
 ifeq ($(CONFIG_SPL_BUILD),)
-obj-$(CONFIG_UNIT_TEST) += boot/
+obj-$(CONFIG_$(SPL_)UT_BOOTSTD) += boot/
 obj-$(CONFIG_UNIT_TEST) += common/
 obj-y += log/
 obj-$(CONFIG_$(SPL_)UT_UNICODE) += unicode_ut.o
diff --git a/test/cmd_ut.c b/test/cmd_ut.c
index 60cd049..1b934b2 100644
--- a/test/cmd_ut.c
+++ b/test/cmd_ut.c
@@ -57,7 +57,7 @@
 #ifdef CONFIG_CMD_BDI
 	U_BOOT_CMD_MKENT(bdinfo, CONFIG_SYS_MAXARGS, 1, do_ut_bdinfo, "", ""),
 #endif
-#ifdef CONFIG_BOOTSTD
+#ifdef CONFIG_UT_BOOTSTD
 	U_BOOT_CMD_MKENT(bootstd, CONFIG_SYS_MAXARGS, 1, do_ut_bootstd,
 			 "", ""),
 #endif