Claude review: drm/bridge: Implement generic USB Type-C DP HPD bridge

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

Patch Review

This creates a new module that listens for typec bus events and auto-registers DP HPD bridges when a DP altmode device appears on a Type-C port.

**Issue (medium): Error return from `drm_dp_hpd_bridge_register()` is ignored.**

```c
if (is_typec_port_altmode(&alt->dev) && alt->svid == USB_TYPEC_DP_SID)
    drm_dp_hpd_bridge_register(alt->dev.parent->parent,
                               to_of_node(alt->dev.parent->fwnode));
```

If bridge registration fails, the caller silently ignores it. At minimum a `dev_err()` or returning `NOTIFY_BAD` would help debugging.

**Issue (minor): `to_typec_altmode()` is called unconditionally on every BUS_NOTIFY_ADD_DEVICE.** This is called for every device on the typec bus, not just altmode devices. If the cast is invalid for non-altmode devices (e.g. typec_port, typec_partner), this could access garbage. The `is_typec_port_altmode()` check happens after the cast. Normally this works because `container_of` is just pointer arithmetic, but it's fragile. Consider checking the device type first.

**Observation:** The `module_exit` function is missing `__exit` annotation:
```c
static void drm_aux_hpd_typec_dp_bridge_module_exit(void)
```
Should be `static void __exit`.

**Observation:** The module has no `MODULE_AUTHOR()`.

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