dt-bindings: vendor-prefixes: add thwc

Shenzhen Tong Heng Wei Chuang Technology Co., Ltd. (hereinafter referred
to as "Tong Heng Wei Chuang") is a focus on wireless communications
equipment brand manufacturers.

Link: http://www.szthwc.com/en/about.html


Signed-off-by: Yang Xiwen <forbidden405@foxmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>