drm/i915/icl: add dummy DSI GPIO element execution function

Add dummy debug logging GPIO element execution function for ICL.

Reviewed-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/f59009ea0a0ebc489a5ec66f387d9dcf7264141f.1543500286.git.jani.nikula@intel.com