Claude review: drm/msm/adreno: Trust the SSoT UBWC config

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Patch Review

From Konrad Dybcio. Removes the entire `a6xx_calc_ubwc_config()` function which had per-GPU hardcoded `highest_bank_bit` and `ubwc_swizzle` overrides, and drops the `_ubwc_config` mutable copy:

```c
-	/* Copy the data into the internal struct to drop the const qualifier (temporarily) */
-	*cfg = *common_cfg;
-
-	/* Use common config as is for A8x */
-	if (!adreno_is_a8xx(gpu)) {
-		cfg->ubwc_swizzle = 0x6;
-		cfg->highest_bank_bit = 15;
-	}
```

This is a significant simplification that trusts the central UBWC config database. The removed `DRM_WARN_ONCE` for mismatched values was previously useful for validation but is no longer needed if the database is authoritative. Good cleanup. Has appropriate R-b tags.

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