drm: Print some debug/error info during DP dual mode detect

drm: Print some debug/error info during DP dual mode detect

There's at least one LSPCON device that occasionally returns an unexpected
adaptor ID which leads to a failed detect. Print some debug info to help
debugging this and future cases. Also print an error for an unexpected
adaptor ID, so users can report it.

v2:
- s/adapter/adaptor/ and add code comment about incorrect type 1 adaptor
  IDs. (Ville)

Cc: dri-devel@lists.freedesktop.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1477499359-12001-1-git-send-email-imre.deak@intel.com