test: CONFIG_UT_BOOTSTD must depend on CONFIG_BOOTSTD

Building sandbox_defconfig with

    CONFIG_BOOTSTD=n
    CONFIG_UT_BOOTSTD=y

leads to an error

    /usr/bin/ld: test/cmd_ut.o:(.data.rel.cmd_ut_sub+0xc0):
    undefined reference to `do_ut_bootstd'

Add the missing dependency.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/Kconfig b/test/Kconfig
index e842c01..e2ec099 100644
--- a/test/Kconfig
+++ b/test/Kconfig
@@ -67,7 +67,7 @@
 
 config UT_BOOTSTD
 	bool "Unit tests for standard boot"
-	depends on UNIT_TEST && SANDBOX
+	depends on UNIT_TEST && BOOTSTD && SANDBOX
 	default y
 
 config UT_COMPRESSION