Claude review: drm/amdgpu: hook up ZONE_DEVICE registration in device init and reset

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

Patch Review

**Unnecessary `#if IS_ENABLED` guards:**
```c
#if IS_ENABLED(CONFIG_DRM_AMDGPU_SVM)
	amdgpu_svm_migration_init(adev);
#endif
```
The header already provides a static inline stub returning 0 when `CONFIG_DRM_AMDGPU_SVM` is disabled. The `#if` guard is redundant and adds visual noise. Just call the function directly.

**Return value of `amdgpu_svm_migration_init` is ignored** in both callsites. If initialization fails (e.g., `devm_memremap_pages` fails), the device will continue without VRAM migration support. The cover letter says `adev->apagemap` is NULL when disabled, and the helper functions check for this, so this is likely intentional — but a `dev_warn` on failure would help debugging.

**In the reset path:**
```c
if (!tmp_adev->kfd.init_complete) {
#if IS_ENABLED(CONFIG_DRM_AMDGPU_SVM)
	amdgpu_svm_migration_init(tmp_adev);
#endif
	kgd2kfd_init_zone_device(tmp_adev);
```
`amdgpu_svm_migration_init` has an early-return check `if (adev->apagemap && adev->apagemap->initialized) return 0;` — so calling it again after reset is safe. Good.

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Generated by Claude Code Patch Reviewer