Claude review: drm/amdkfd: Add batch MMU notifier support

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

Patch Review

**Overview:** Implements MMU notifier for batch allocations.

**Issues:**

1. **Race Condition - Critical:**
After unlocking `notifier_lock`, the code continues to access `mem`:
```c
+	mutex_unlock(&process_info->notifier_lock);
+	mem->invalid++;
```
There's a TOCTOU (time-of-check-time-of-use) issue if `mem` can be freed between the check and increment.

2. **Return Value Ignored:**
```c
+static bool amdgpu_amdkfd_invalidate_userptr_batch(...)
+{
+	amdgpu_amdkfd_evict_userptr_batch(mni, range, cur_seq);
+	return true;
+}
```
Always returns true even if eviction failed. The caller might need to know about failures.

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Generated by Claude Code Patch Reviewer