drm/i915/bios: log about presence of DSI sequences we do not run

Leave behind some debugging clues in case some panels don't work
properly.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/b36302b24676af511f4bbf702be21cc7e8f987c2.1474286487.git.jani.nikula@intel.com