Claude review: drm/msm/a6xx: Allow IFPC with perfcntr stream

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

Patch Review

Changes `sysprof_setup` to accept `bool force_on` and calls it from `sample_worker` to inhibit IFPC only during register reads:

```c
/* Inhibit IFPC while accessing registers: */
if (gpu->funcs->sysprof_setup)
    gpu->funcs->sysprof_setup(gpu, true);
// ... read counters ...
/* Re-enable IFPC: */
if (gpu->funcs->sysprof_setup)
    gpu->funcs->sysprof_setup(gpu, false);
```

The `msm_gpu_sysprof_no_ifpc` now only checks `sysprof_active` (legacy userspace path), not the perfcntr stream, since IFPC is now handled dynamically for streams. Clean separation.

The `msm_context_set_sysprof` call is correctly updated to pass `false` for `force_on`.

---

**Summary of findings:**

- **One bug**: `msm_perfcntrs_stream_read` returns 0 (EOF) instead of `-EAGAIN` when `O_NONBLOCK` is set and no data is available.
- The rest of the series is well-engineered with careful attention to locking, barrier ordering, and power management synchronization.

---
Generated by Claude Code Patch Reviewer