dt-bindings: Add vendor prefix for DLC Display Co., Ltd.

DLC provides a wide range of display solutions.
Website: http://www.dlcdisplay.com/

Signed-off-by: Philipp Zabel <[e-mail]>
Signed-off-by: Marco Felsch <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/vendor-prefixes.txt

···
 digi	Digi International Inc.
 digilent	Diglent, Inc.
 dioo	Dioo Microcircuit Co., Ltd
+dlc	DLC Display Co., Ltd.
 dlg	Dialog Semiconductor
 dlink	D-Link Corporation
 dmo	Data Modul AG