argument: Fix readability-braces-around-statements

```
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:41:52: error: statement should be inside braces [readability-braces-around-statements,-warnings-as-errors]
        while ((i->val != option) && (i->val != 0))
                                                   ^
                                                    {
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:44:20: error: statement should be inside braces [readability-braces-around-statements,-warnings-as-errors]
        if (i->val)
                   ^
                    {
```

Change-Id: I691e28572d5807cea03faf69a9234e1546a9eb61
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/argument.cpp b/argument.cpp
index 0d24112..563bcfb 100644
--- a/argument.cpp
+++ b/argument.cpp
@@ -42,10 +42,14 @@
 
         const auto* i = &options[0];
         while ((i->val != option) && (i->val != 0))
+        {
             ++i;
+        }
 
         if (i->val)
+        {
             arguments[i->name] = (i->has_arg ? optarg : true_string);
+        }
     }
 }