Claude review: bus: mhi: Move sahara protocol driver under drivers/bus/mhi

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

Patch Review

Relocates the Sahara driver to `drivers/bus/mhi/sahara/` and makes it a standalone module.

**Issues:**

- **Bug: `qaic_init()` error handling is broken.** The goto labels are swapped after removing `sahara_register()`:
  ```c
  ret = pci_register_driver(&qaic_pci_driver);
  if (ret) {
      pr_debug("qaic: pci_register_driver failed %d\n", ret);
      goto free_pci;  // BUG: calls pci_unregister_driver on never-registered driver
  }

  ret = mhi_driver_register(&qaic_mhi_driver);
  if (ret) {
      pr_debug("qaic: mhi_driver_register failed %d\n", ret);
      goto free_mhi;  // BUG: calls mhi_driver_unregister on never-registered driver
  }
  ```
  Correct behavior: `pci_register_driver` failure should `return ret` directly; `mhi_driver_register` failure should `goto free_pci`.

- **SPDX license changed** from `GPL-2.0-only` to `GPL-2.0` and copyright changed from "2024 Qualcomm Innovation Center" to "2018-2020, The Linux Foundation". This needs justification in the commit message.

- **Kconfig forces `FW_LOADER_COMPRESS_XZ` and `FW_LOADER_COMPRESS_ZSTD`** unconditionally. This imposes decompression dependencies on all users. Should this be optional?

- **Dead declarations in `include/linux/sahara.h`**: `sahara_register()`/`sahara_unregister()` are now wrapped in `module_init`/`module_exit` but still declared in the public header. QAIC no longer calls them.

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Generated by Claude Code Patch Reviewer