test: sysfs: Fix readability-braces-around-statements

```
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../test/sysfs.cpp:46:28: error: statement should be inside braces [readability-braces-around-statements,-warnings-as-errors]
        if (dir == nullptr)
                           ^
                            {
```

Change-Id: Ib36d16ad9c7b716b397ba95fb13aa2d41ec1f195
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
1 file changed