of: Add vendor prefix for Tianma Micro-electronics

Tianma Micro-electronics Co., Ltd. (Tianma) specializes in providing
display solutions and efficient support services worldwide.

More info:
http://en.tianma.com/about.shtml

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -296,6 +296,7 @@ technologic	Technologic Systems
 terasic	Terasic Inc.
 thine	THine Electronics, Inc.
 ti	Texas Instruments
+tianma	Tianma Micro-electronics Co., Ltd.
 tlm	Trusted Logic Mobility
 topeet  Topeet
 toradex	Toradex AG