modetest: Reduce the length of the connector type string

Spelling out eDP or DP make for a ridicilously long string which plays
havoc with formatting. Just say eDP or DP.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>