test: sandbox: fix invalid_use_of_IF_ENABLED_INT if BLOBLIST=n

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>