[clang] [flang] [flang] Add UNSIGNED (PR #113504)

[Daniel Chen via cfe-commits]

DanielCChen wrote:

Seems a place that needs to add UNSIGNED type case
```
llvm-project/flang/lib/Semantics/resolve-names.cpp:7597:16: error: enumeration value 'Unsigned' not handled in switch [-Werror,-Wswitch]
  switch (type.category()) {
          ~~~~~^~~~~~~~~~
llvm-project/flang/lib/Semantics/resolve-names.cpp:7621:1: error: non-void function does not return a value in all control paths [-Werror,-Wreturn-type]
}
```


https://github.com/llvm/llvm-project/pull/113504