drm/i915: extract connector update from intel_ddc_get_modes() for reuse

commit 4eab81366465aedcfd26de960c595bc03599c09f upstream.

Refactor the connector update part of intel_ddc_get_modes() into a separate
intel_connector_update_modes() function for reuse. No functional changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=45881
Tested-by: Alex Ferrando <alferpal@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>