Claude review: drm/amd/display: Fix DDC register assignment type errors

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

Patch Review

**Correctness:** The change is correct. The parameter types are changed from the non-existent `struct ddc_shift` / `struct ddc_mask` to `struct ddc_sh_mask`, which matches:
- The actual struct definition in `ddc_regs.h:130`
- The `hw_ddc` struct fields in `hw_ddc.h:34-35` (`const struct ddc_sh_mask *shifts` / `*masks`)
- All callers across every DCN/DCE generation

```c
-		const struct ddc_shift *shift,
-		const struct ddc_mask *mask)
+		const struct ddc_sh_mask *shift,
+		const struct ddc_sh_mask *mask)
```

**Nit on commit message:** The commit message says "Fix invalid type assignments in ddc_sh_mask" which is slightly misleading — the fix is in the *function parameter declarations*, not in `ddc_sh_mask` itself. Something like "Fix parameter type mismatches in dcn_define_ddc_registers_common()" would be clearer. This is minor and not a blocker.

**Note:** The `hw_factory_dcn_ddc.h` file doesn't exist in the current drm-next tree I have access to, so the patch didn't apply. This likely depends on an earlier patch that introduced this file (and the bug along with it). The fix itself is valid regardless.

**Reviewed-by worthy:** Yes, this is a simple, correct type fix.

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