tree-wide: move `unsigned` to the start of type declaration

tree-wide: move `unsigned` to the start of type declaration

Even though ISO C11 doesn't mandate in which order the type specifiers
should appear, having `unsigned` at the beginning of each type
declaration feels more natural and, more importantly, it unbreaks
Coccinelle, which has a hard time parsing `long unsigned` and others:

```
init_defs_builtins: /usr/lib64/coccinelle/standard.h
init_defs: /home/mrc0mmand/repos/systemd/coccinelle/macros.h
HANDLING: src/shared/mount-util.c
: 1: strange type1, maybe because of weird order: long unsigned
```

Most of the codebase already "complies", so let's fix the remaining
"offenders".