Claude review: drm/tyr: Remove custom register struct

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

Clean removal of the now-unused `Register<OFFSET>` struct, its `read`/`write` methods, and associated imports. After patches 1, 3, and 4 converted all users, this is purely mechanical cleanup.

```rust
-pub(crate) struct Register<const OFFSET: usize>;
-impl<const OFFSET: usize> Register<OFFSET> {
-    pub(crate) fn read(...) -> Result<u32> { ... }
-    pub(crate) fn write(...) -> Result { ... }
-}
```

No issues. This is ordered correctly in the series -- all users are converted first, then the old infrastructure is removed.

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