[llvm] [CodeGen] Simplify LLT bitfields. NFC. (PR #120074)

[Tim Gymnich via llvm-commits]

https://github.com/tgymnich approved this pull request.

Looks good!
I made some ASCII art to illustrate the memory layout.

```c++
/*
 63       56       47       39       31       23       15       7      0
 |        |        |        |        |        |        |        |      |
|xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|
 +++                                                                        (1)
    ....................................                                    (2)
    ******************                                                      (3)
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~                           (4)
                                                 ^^^^^^^^^^^^^^^^^^         (5)
                                                                       @    (6)

(1) Kind  (2) ScalarSize  (3) PointerSize  (4) PointerAddressSpace 
(5) VectorElements  (6) VectorScalable
*/
```

https://github.com/llvm/llvm-project/pull/120074