test: sandbox: fix invalid_use_of_IF_ENABLED_INT if BLOBLIST=n

Having CONFIG_OF_EMBED=y && CONFIG_BLOBLIST=n leads to the link
error:
```
ld: /tmp/ccRVty.ltrans40.ltrans.o: in function `lib_test_is_enabled':
test/lib/kconfig.c:24: undefined reference to \
                                       `invalid_use_of_IF_ENABLED_INT'
ld: test/lib/kconfig.c:26: undefined reference to \
                                `invalid_use_of_CONFIG_IF_ENABLED_INT'
```

Fixes: 29784d62ede ("test: Add some tests for kconfig.h")
Signed-off-by: Evgeny Bachinin <EABachinin@salutedevices.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/lib/kconfig.c b/test/lib/kconfig.c
index 0c463bb..a3645ab 100644
--- a/test/lib/kconfig.c
+++ b/test/lib/kconfig.c
@@ -21,10 +21,12 @@
 	ut_asserteq(0, CONFIG_IS_ENABLED(OF_PLATDATA));
 	ut_asserteq(0, CONFIG_IS_ENABLED(_UNDEFINED));
 
-	ut_asserteq(0xb000,
-		    IF_ENABLED_INT(CONFIG_BLOBLIST_FIXED, CONFIG_BLOBLIST_ADDR));
-	ut_asserteq(0xb000,
-		    CONFIG_IF_ENABLED_INT(BLOBLIST_FIXED, BLOBLIST_ADDR));
+	if (IS_ENABLED(CONFIG_BLOBLIST)) {
+		ut_asserteq(0xb000, IF_ENABLED_INT(CONFIG_BLOBLIST_FIXED,
+						   CONFIG_BLOBLIST_ADDR));
+		ut_asserteq(0xb000, CONFIG_IF_ENABLED_INT(BLOBLIST_FIXED,
+							  BLOBLIST_ADDR));
+	}
 
 	/*
 	 * This fails if CONFIG_TEST_KCONFIG_ENABLE is not enabled, since the