drm/i915/psr: switch PSR debugfs to struct intel_connector

Prefer struct intel_connector over struct drm_connector.

Cc: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230317134144.223936-2-jani.nikula@intel.com