Claude review: drm/bridge: synopsys: dw-dp: Support software triggered OOB HPD

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

Patch Review

Adds `hpd_sw_sel` and `hpd_sw_cfg` function pointers to `dw_dp_plat_data`:

```c
+	void *data;
+	void (*hpd_sw_sel)(void *data, bool hpd);
+	void (*hpd_sw_cfg)(void *data, bool hpd);
```

**Issue — `dw_dp_bridge_oob_notify` always logs an error if no platform handler:**
```c
+	if (dp->plat_data.hpd_sw_cfg)
+		dp->plat_data.hpd_sw_cfg(dp->plat_data.data, hpd_high);
+	else
+		dev_err_once(dp->dev, "Missing platform handler for OOB HPD handling\n");
```
The `oob_notify` callback is unconditionally registered in `dw_dp_bridge_funcs`, so any platform using this bridge that receives an OOB event without implementing `hpd_sw_cfg` will get an error. Since `oob_notify` is only called for USB-C scenarios and the callback is only invoked if the connector gets an OOB event, this is probably fine in practice. But it might be cleaner to only register `oob_notify` when the platform provides the handlers.

**`dw_dp_is_routed_to_usb_c`** uses `drm_bridge_chain_get_last_bridge` with `__free(drm_bridge_put)` — the cleanup annotation is good.

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