[flang][cuda] Allow object with SHARED attribute as definable (#82822)

A semantic error was raised in device subprogram like: 

```
attributes(global) subroutine devsubr2()
   real, shared :: rs
   rs = 1
end subroutine
```

Object with the SHARED attribute can be can be read or written by all
threads in the block.


https://docs.nvidia.com/hpc-sdk/archive/24.1/compilers/cuda-fortran-prog-guide/index.html#cfpg-var-qual-attr-shared