physical: Fix cert-dcl59-cpp

```
../physical.hpp:19:1: error: do not use unnamed namespaces in header files [cert-dcl59-cpp,-warnings-as-errors]
namespace
^
```

Change-Id: I8e663e42604c9f813c3f8febeb7e5bdb6ac0262b
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
1 file changed